A flow battery stack end plate joint and stack thereof

Abstract

The utility model relates to a kind of liquid flow battery stack end plate joint and its stack, the joint includes: sealing element, joint body, with electrolyte contact and with the sealing element cooperation, the joint body includes first connecting part and second connecting part, the first connecting part is used to insert the preset through-hole of stack end plate, first connecting part sets the groove of accommodating the sealing element;Electrolyte flow channel is passed through in the second connecting part and first connecting part, the first assembly hole corresponding with the preset threaded hole of end plate is equipped in joint body outer periphery;Rigid protection member;The electrolyte inlet and outlet of the stack end plate is equipped with counterbore, the bottom of the counterbore is equipped with the preset through-hole adapted with the first connecting part, the bottom of the counterbore is also equipped with preset threaded hole;The joint body is assembled in counterbore, sealing element is embedded in the groove of first connecting part, rigid protection member is coaxially sleeved on the outside of second connecting part by adaptive hole, the fixation of joint body and rigid protection member is realized by fastener.

Description

Technical Field

[0001] This utility model relates to the field of flow battery technology, and more specifically, to a flow battery stack end plate connector and the flow battery stack. Background Technology

[0002] With the advocacy of carbon neutrality and the surge in national enthusiasm for carbon reduction, the vigorous development of renewable energy grid connection to replace traditional fossil fuels has been elevated to the level of national energy strategy. Developing a new type of integrated power system encompassing generation, grid, load, and storage is the technological path to achieving carbon neutrality. Developing high-efficiency, low-cost energy storage devices and overcoming material and structural limitations in energy storage technology have become key supporting technologies for developing integrated power systems. Among numerous energy storage technologies, vanadium redox flow battery technology, with its outstanding safety, power-capacity decoupling, deep charging and discharging capabilities, and environmental friendliness, is highly suitable for large-scale, long-term energy storage and has become one of the most promising energy storage technologies.

[0003] The battery stack is the core component of a vanadium redox flow battery energy storage system, determining the system's performance and reliability. Preventing electrolyte leakage from the stack, especially by addressing weak points in the electrolyte flow path, is essential for improving stack reliability. The electrolyte flows in and out of the stack through connectors integrated into the stack endplates. These connectors must not only fit tightly with seals to prevent electrolyte leakage to the current collector and subsequent corrosion, but also be compatible with external valves or pipes to prevent external leakage. Therefore, both sealing design and structural strength must be considered to prevent breakage of the stack connectors during compression, vibration, and transportation. Especially to prevent corrosion from sulfuric acid solutions, endplate connectors are often made of plastic, which has poor strength, is prone to breakage, and is difficult to repair after damage. Therefore, structural design must consider both protection and ease of maintenance.

[0004] Existing patent documents, such as the vanadium redox flow battery stack end plate disclosed in CN205863303U, focus on grooves on the side of the end plate to prevent leakage at the edge between the end plate and the external structure. They do not address the connector structure for the electrolyte inlet and outlet, and therefore cannot solve the problems of connector breakage, maintenance, and current collector corrosion. CN201985208U discloses a flow battery stack structure with an insulating plate inlet, where the electrolyte inlet and outlet are located on a multi-channel insulating plate, and the end plate only serves a fixing function. It does not address the protection, sealing, or maintenance structure of the connectors on the end plate. CN105... The end plate of the flow battery stack disclosed in 322198A and its preparation method enhance the overall rigidity of the end plate by optimizing the reinforcing ribs and mounting holes on the end plate to prevent deformation. The focus is on the structural reinforcement of the end plate itself, and it does not involve the connector assembly of the electrolyte inlet and outlet. The fixing structure of the all-vanadium redox flow battery stack disclosed in CN206497947U is based on the hollow bolts with inserted parts to prevent loosening. It is a fixing bolt structure for the stack, which is not related to the connector structure of the electrolyte inlet and outlet, and cannot solve the problems of joint breakage prevention, sealing and maintenance.

[0005] In summary, none of the existing technologies address the integrated structural design of electrolyte inlet and outlet joint protection, external detachable assembly, and sealing and corrosion protection on the endplate of the flow battery stack. Targeted solutions are needed to address these issues. Utility Model Content

[0006] To address the problems of easy breakage of plastic in existing flow battery stack end plate connectors, the need to disassemble the stack for maintenance, and corrosion of the current collector plate due to seal failure, this utility model provides a flow battery stack end plate connector and its stack. Through structural design, the connector is designed to prevent breakage, facilitate maintenance, and ensure reliable sealing.

[0007] The technical means adopted in this utility model are as follows: A flow battery stack end plate connector is disposed on the end plate of the stack. The connector includes: Seals are used to prevent electrolyte leakage to the manifold; The connector body is in contact with the electrolyte and mates with the sealing element. The connector body includes a first connecting part and a second connecting part. The first connecting part is used to insert into a preset through hole in the end plate of the fuel cell stack. The first connecting part is provided with a groove to accommodate the sealing element. The second connecting part and the first connecting part are connected by an electrolyte flow channel. The outer periphery of the connector body is provided with a first assembly hole corresponding to the preset threaded hole in the end plate. A rigid protective component is used to protect the connector body and provide rigid support. The rigid protective component is sleeved on the outside of the connector body. The rigid protective component is provided with an adaptation hole that is adapted to the second connecting part. The outer periphery of the rigid protective component is provided with a second assembly hole that corresponds to the position of the first assembly hole. The electrolyte inlet and outlet of the stack end plate are provided with countersunk holes. The bottom of the countersunk holes is provided with a preset through hole adapted to the first connecting part, and the bottom of the countersunk holes is also provided with a preset threaded hole. The connector body is assembled in the countersunk hole, the sealing element is embedded in the groove of the first connecting part, and the rigid protective element is coaxially sleeved on the outside of the second connecting part through the matching hole. The fastener passes through the second assembly hole and the first assembly hole in sequence and then cooperates with the preset threaded hole of the end plate to fix the connector body and the rigid protective element.

[0008] Furthermore, the sealing element is a sealing O-ring, the connector body is a plastic connector, and the rigid protective element is a stainless steel sleeve; the sealing O-ring is interference-fitted with the groove of the first connecting part, and the first connecting part of the plastic connector is clearance-fitted with the preset through hole at the bottom of the countersunk hole of the end plate.

[0009] Furthermore, the adapter hole of the stainless steel sleeve is clearance-fitted with the second connecting part of the plastic connector, and the inner wall of the stainless steel sleeve is in contact with the outer peripheral surface of the plastic connector.

[0010] Furthermore, the end face of the stainless steel sheath away from the adapter hole is flush with the open end face of the countersunk hole of the fuel cell stack end plate, and the fastener is a bolt, which is threadedly connected to the pre-set threaded hole of the end plate.

[0011] Furthermore, the diameter of the first connecting part of the connector body is smaller than the diameter of the second connecting part, and the diameter of the adapter hole of the rigid protective member is adapted to the outer diameter of the second connecting part, ensuring that there is no offset when the rigid protective member is sleeved along the axial direction.

[0012] This utility model also discloses a flow battery stack, including the above-mentioned flow battery stack end plate connector, and also includes current collectors and single battery packs. The stack end plates are disposed at both ends of the stack along the axial direction. The current collectors are respectively attached to the inner sidewalls of the two stack end plates. The single battery packs are stacked between the two current collectors. After the first connecting part of the connector body of the end plate connector passes through the pre-set through hole of the end plate, its end face does not extend beyond the side of the end plate facing the current collector.

[0013] Furthermore, the stack end plate, current collector, and single battery pack are axially fixed by a clamping mechanism, and the rigid protective component of the end plate joint does not extend beyond the outer wall of the stack end plate to avoid interference with external structures.

[0014] Compared with the prior art, the present invention has the following advantages: 1. The stainless steel sleeve of this invention is fitted onto the outside of the plastic joint in a fully circumferential manner. The inner wall of its cylindrical body is tightly fitted with the outer circumferential surface of the plastic joint, forming a rigid constraint surface. Simultaneously, the positioning boss of the stainless steel sleeve precisely engages with the second connecting part of the plastic joint through a coaxial adapter hole, ensuring that no radial displacement occurs after installation. This structure allows the rigidity of the stainless steel sleeve to be fully transferred to the plastic joint. When facing lateral or forward impacts, the stainless steel sleeve can directly resist external loads, preventing the plastic joint from being directly stressed. For vibration conditions, the stainless steel sleeve can limit the displacement of the plastic joint, reducing fatigue damage. Compared to existing unprotected plastic joints, this invention significantly improves the joint's impact and vibration resistance, fundamentally solving the problem of fracture caused by insufficient rigidity in plastic joints and extending the joint's service life.

[0015] 2. The sealing O-ring, plastic connector, and stainless steel sleeve of this utility model are all designed for assembly on the outside of the end plate. Installation and disassembly of all components do not require disassembling the current collector or individual cell pack inside the fuel cell stack. During assembly, simply insert the sealing O-ring into the groove of the plastic connector boss, insert the plastic connector into the countersunk hole of the end plate, and then fit the stainless steel sleeve and secure it with bolts. The entire process is completed on the outside of the end plate. If the plastic connector breaks accidentally, the repair process involves removing the bolts, removing the stainless steel sleeve, taking out the damaged plastic connector and O-ring, replacing them with new parts, and reassembling. This does not require touching the internal structure of the fuel cell stack. Compared to existing end plate connectors, which require assembly from the inside of the fuel cell stack and require disassembly for repairs, potentially leading to stack positioning errors and material damage, this utility model, through its external maintenance system design, completely avoids the risks associated with disassembling the fuel cell stack, significantly shortens repair time, reduces maintenance costs, and improves the ease of operation and maintenance of the fuel cell stack.

[0016] 3. The sealing O-ring of this utility model is embedded in the groove of the first boss of the plastic connector and forms an interference fit with the through hole at the bottom of the countersunk hole of the end plate. The boss groove of the plastic connector provides accurate positioning for the sealing O-ring, avoids sealing failure caused by O-ring displacement, fundamentally avoids the current collector plate being corroded by electrolyte, and ensures the stability and service life of the internal structure of the fuel cell stack. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram showing the assembly position relationship between the existing fuel cell stack end plates and connectors.

[0019] Figure 2 A 3D view of the front of an existing plastic connector.

[0020] Figure 3 A 3D view of the back of an existing plastic connector.

[0021] Figure 4 This utility model presents a schematic diagram of the assembly position relationship between an end plate and a connector.

[0022] Figure 5 The three-dimensional front view of the stainless steel sheath proposed in this utility model.

[0023] Figure 6 The three-dimensional view of the back of the stainless steel sheath proposed in this utility model.

[0024] Figure 7 The three-dimensional front view of the plastic connector proposed in this utility model.

[0025] Figure 8 Three-dimensional view of the back side of the plastic connector proposed in this utility model.

[0026] Figure 9 This is a cross-sectional view of the variable diameter flow channel 16 in an embodiment of this utility model.

[0027] Figure 10 This is the back side of the connector of the variable diameter structure of the flow channel 16 in this embodiment of the present invention.

[0028] Figure 11 This is a cross-sectional view of the variable diameter flow channel 16 in an embodiment of this utility model.

[0029] Figure 12 This is the back side of the connector of the variable diameter structure of the flow channel 16 in this embodiment of the present invention.

[0030] In the figure: 1. Through hole for inserting a plastic connector into an existing fuel cell stack end plate; 2. Existing plastic connector; 3. Boss for inserting into the through hole of the existing end plate; 4. Groove for installing a sealing O-ring; 5. Countersunk hole for electrolyte inlet and outlet of the end plate; 6. Through hole at the bottom of the countersunk hole of the end plate; 7. Internal threaded hole at the bottom of the countersunk hole of the end plate; 8. Plastic connector of this utility model; 9. Stainless steel sleeve of this utility model; 10. Boss of the stainless steel sleeve; 11. Assembly hole on the surface of the stainless steel sleeve outside the boss, coaxial with the threaded hole in the countersunk hole of the end plate; 12. Boss of the plastic connector away from the bottom of the countersunk hole; 13. Assembly hole on the surface of the plastic connector outside the boss, coaxial with the threaded hole in the countersunk hole of the end plate; 14. Boss of the plastic connector facing the bottom of the countersunk hole; 15. Groove for installing a sealing O-ring on the boss; 16. Through hole for electrolyte flow channel on the plastic connector. Detailed Implementation

[0031] It should be noted that, where there is no conflict, the embodiments and features in the embodiments of this utility model can be combined with each other. The present utility model will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this utility model or its application or use. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0035] In the description of this utility model, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0036] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0037] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this utility model.

[0038] The assembly relationship between the end plates and connectors of the existing flow battery stack is as follows: Figures 1-3 As shown, the plastic connector 2 extends from the through hole 1 inside the end plate to the outside of the end plate, where it is then bonded or welded to external pipes or valves, serving as a guide for the electrolyte inlet and outlet. One end of the connector is a boss 3, and the other end has a groove 4 for accommodating O-rings. As can be seen from the assembly relationship, the plastic connector is unprotected and easily damaged by side impacts, leading to breakage of the outer connector of the fuel cell stack. Once broken, it cannot be repaired from the outside of the fuel cell stack; the stack must be disassembled for repair. Re-clamping the fuel cell stack after disassembly carries the risk of positioning deviation and material damage.

[0039] Therefore, such as Figures 4-8 As shown in the figure, this utility model embodiment discloses a flow battery stack end plate connector, which is disposed on the end plate of the stack. The connector includes: The sealing element is used to prevent electrolyte leakage to the current collector, forming a radial sealing barrier for the electrolyte. Through its adaptation with the connector body, it forms a tight seal, preventing electrolyte leakage from the gap between the connector and the end plate to the current collector inside the stack, ensuring the current collector is not corroded by the electrolyte. In this embodiment, the sealing element is a fluororubber sealing ring to cope with the operating environment of the flow battery. The connector body is in contact with the electrolyte and cooperates with the sealing element. The connector body includes a first connecting part and a second connecting part. The first connecting part is used to insert into a preset through hole in the fuel cell end plate. The first connecting part is provided with a groove to accommodate the sealing element. The second connecting part and the first connecting part are connected by an electrolyte flow channel 16.

[0040] The outer periphery of the connector body is provided with a first assembly hole 13 corresponding to the pre-set threaded hole of the end plate; the first connecting part is a boss structure 14 of the plastic connector facing the bottom of the countersunk hole, and the second connecting part is a boss structure of the plastic connector away from the bottom of the countersunk hole.

[0041] A rigid protective component is used to protect the connector body and provide rigid support, forming a full-circumferential rigid constraint on the connector body to resist external impacts and vibration loads and prevent the connector body from breaking due to insufficient rigidity. The inner wall of the cylindrical protective body forms a tightly fitting constraint surface with the outer circumferential surface of the connector body, realizing full-length support for the connector body. The positioning boss has a coaxial positioning hole that matches the shape of the second connecting part of the connector body, ensuring that the rigid protective component and the connector body are precisely coaxially fitted together and avoiding assembly misalignment. The rigid protective component is fitted on the outside of the connector body. The rigid protective component has an adaptation hole that matches the second connecting part, and a second assembly hole 11 corresponding to the position of the first assembly hole is provided on the outer circumference of the rigid protective component. The stainless steel sleeve is provided with a stainless steel sleeve boss 10 to achieve all-round protection for the connector body.

[0042] The end plate of the fuel cell stack has countersunk holes 5 at the electrolyte inlet and outlet, forming a stepped mounting cavity. The bottom of the countersunk hole has a pre-set through hole 6 adapted to the first connecting part, and a pre-set threaded hole 7. The connector body is assembled within the countersunk hole, the seal is embedded in the groove 15 of the first connecting part, and the rigid protective component is coaxially sleeved on the outside of the second connecting part through an adapter hole. Fasteners pass through the second assembly hole and the first assembly hole in sequence, and then engage with the pre-set threaded hole on the end plate to fix the connector body and the rigid protective component. The fasteners are bolts, which form an integrated fixing unit between the connector body and the rigid protective component, and lock this unit within the stepped mounting cavity of the fuel cell stack end plate. Specifically, the bolts pass through the second assembly hole of the rigid protective component and the first assembly hole of the connector body in sequence, and then form a threaded connection with the internal threaded hole of the end plate. The entire assembly and disassembly process can be completed from the outside of the end plate, constructing an externally detachable maintenance system that does not require disassembly of the fuel cell stack.

[0043] In this embodiment, the plastic connector is a corrosion-resistant plastic connector 8.

[0044] The end plate connector structure disclosed in this utility model can improve the impact resistance of the plastic connector through the stainless steel sheath 9, preventing the connector from breaking; it can also be disassembled and replaced outside the fuel cell after the plastic connector breaks accidentally, improving its maintainability; at the same time, the cooperation with the sealing O ring can also prevent the current collector from corroding.

[0045] Furthermore, the sealing element is a sealing O-ring, the connector body is a plastic connector, and the rigid protective element is a stainless steel sleeve; the sealing O-ring is interference-fitted with the groove of the first connecting part, and the first connecting part of the plastic connector is clearance-fitted with the preset through hole at the bottom of the countersunk hole of the end plate.

[0046] Furthermore, the adapter hole of the stainless steel sleeve is clearance-fitted with the second connecting part of the plastic connector, and the inner wall of the stainless steel sleeve is in contact with the outer peripheral surface of the plastic connector.

[0047] As another optional implementation, a buffer layer can be provided on the mating surface of the stainless steel sheath and the plastic joint to buffer external impacts and vibrations during fuel cell operation, reduce fatigue damage to the plastic joint, and the buffer layer also fills the assembly gap to further improve the coaxiality of the two and avoid local stress concentration caused by hard contact, so as to solve the problem of rigid mating.

[0048] Furthermore, the end face of the stainless steel sheath away from the adapter hole is flush with the open end face of the countersunk hole of the fuel cell stack end plate, and the fastener is a bolt, which is threadedly connected to the pre-set threaded hole of the end plate.

[0049] Furthermore, the diameter of the first connecting part of the joint body is smaller than the diameter of the second connecting part, forming an axial stepped surface. The diameter of the adapter hole of the rigid protective component is adapted to the outer diameter of the second connecting part, and the end face of the positioning boss of the rigid protective component fits against the axial stepped surface, ensuring that there is no offset when the rigid protective component is axially fitted. No axial movement occurs after fitting, and it also provides an axial pre-tightening support reference for the fastening component, preventing axial deformation of the joint body during fastening.

[0050] The countersunk hole of the fuel cell stack end plate includes a positioning section and an assembly section; the positioning section is a cylindrical cavity with a small diameter, used to cooperate with the first connecting part of the connector body to achieve precise positioning; the assembly section is a cylindrical cavity with a larger diameter, used to accommodate the cylindrical protective body of the rigid protection component; the coaxiality tolerance control of the positioning section and the assembly section is achieved by integral machining of the end plate, ensuring coaxial assembly of the connector body and the rigid protection component, and avoiding protection failure or sealing leakage due to coaxiality deviation.

[0051] This utility model also discloses a flow battery stack, including the above-mentioned flow battery stack end plate connector, and also includes current collectors and single battery packs. The stack end plates are disposed at both ends of the stack along the axial direction. The current collectors are respectively attached to the inner sidewalls of the two stack end plates. The single battery packs are stacked between the two current collectors. After the first connecting part of the connector body of the end plate connector passes through the pre-set through hole of the end plate, its end face does not extend beyond the side of the end plate facing the current collector.

[0052] Furthermore, the stack end plate, current collector, and single battery pack are axially fixed by a clamping mechanism, and the rigid protective component of the end plate joint does not extend beyond the outer wall of the stack end plate to avoid interference with external structures.

[0053] This invention, through the coordinated design of the sealing element, the connector body, and the rigid protective element, effectively solves the core problems in the prior art, such as the easy breakage of plastic connectors, the need to disassemble the fuel cell for maintenance, and the corrosion of the current collector due to seal failure. However, in practical applications, it has been found that the flow rate and flow uniformity between individual cells are difficult to control when the electrolyte flows through the connector's flow channel. On the one hand, the electrolyte flow rate in a straight channel is slow, resulting in low electrolyte supply efficiency for individual cells within the fuel cell stack, affecting the electrochemical reaction rate. On the other hand, there are differences in the electrolyte distribution among individual cells within the fuel cell stack, leading to incomplete reactions in some cells due to insufficient flow, thus lowering the overall performance of the fuel cell stack. Furthermore, the traditional straight-through channel cannot adapt to the individual flow requirements of individual cells in different positions, limiting further improvements in fuel cell stack performance. Therefore, as a solution to the technical problems in the prior art, this invention further designs a variable-diameter structure in the electrolyte flow channel of the connector body. That is, the electrolyte flow channel can be a straight channel without diameter change or a channel with diameter change, narrowing from the second connection part to the first connection part to increase the flow rate. It is not limited to a uniform narrowing along the channel axis, but can also be set to an eccentric narrowing off the axis, with the channel outlet of the first connection part far away from the electrolyte inlet of the adjacent battery, increasing the electrolyte flow rate of the distant battery, and thus regulating the flow uniformity of each cell in the stack.

[0054] Specifically, such as Figures 9-12 As shown, where Figure 9 , Figure 10 A uniformly tapered structure along the channel axis is shown. Figure 11 , Figure 12The diagram illustrates an off-axis eccentric reduction in diameter. This variable-diameter structure features a reduced diameter from the second connecting portion of the connector body towards the first connecting portion, specifically including two implementation forms: one is a uniform reduction in diameter along the flow channel axis, which smoothly increases the electrolyte flow rate and enhances the electrolyte circulation efficiency within the stack through a gradual change in channel cross-section; the other is an off-axis eccentric reduction in diameter, which moves the channel outlet of the first connecting portion away from the electrolyte inlet of the adjacent single cell, specifically increasing the electrolyte flow rate of the distant target single cell. This variable-diameter structure allows for flexible adaptation to electrolyte flow rate adjustment and single-cell flow distribution requirements, achieving secondary optimization of stack performance.

[0055] Depending on the specific application scenario, this variable diameter structure runs through the first and second connecting parts of the connector body, rather than the traditional equal diameter straight-through structure. For scenarios that require an overall improvement in electrolyte circulation efficiency, a uniform diameter reduction design along the channel axis is adopted. After the electrolyte flows in from the second connecting part with a larger diameter, it gradually accelerates in the diameter reduction section, entering the stack at a faster flow rate and promoting the electrochemical reaction on the electrode surface. For scenarios where the flow distribution within the stack is uneven, an eccentric diameter reduction design off-axis is adopted. By shifting the position of the channel outlet, more electrolyte is directed to the single cells with insufficient flow, making the electrolyte supply of each single cell more balanced.

[0056] The variable diameter structure is integrally formed with the connector body, eliminating the need for additional components. It does not compromise the original connector's sealing performance and rigid protection, while also specifically addressing the optimization of electrolyte flow rate and distribution. This further expands the functional applicability of the end plate connector and improves the overall operational stability and output efficiency of the flow battery stack.

[0057] The installation sequence of this utility model is as follows: A countersunk hole is provided at the electrolyte inlet / outlet position of the fuel cell stack end plate to accommodate the plastic connector. The bottom of the countersunk hole is provided with a through hole and an internal threaded hole.

[0058] The aforementioned plastic connector is shaped to fit the countersunk hole of the fuel cell stack end plate and can be placed at the bottom of the countersunk hole. A boss is provided on the plastic connector facing the bottom of the countersunk hole, and the boss can be inserted into a through hole at the bottom of the end plate countersunk hole. A structure for accommodating a sealing O-ring is provided on the top of this boss for installing and positioning the O-ring; a boss is also provided on the plastic connector away from the bottom of the countersunk hole, and a through hole is provided on this boss to pass through the entire plastic connector as an electrolyte flow channel. A through hole is provided on the outer surface of the plastic connector, at the same position as the internal threaded hole of the end plate.

[0059] The aforementioned stainless steel sheath is shaped to fit the countersunk hole on the fuel cell stack end plate and can be fitted onto the plastic connector on the side away from the countersunk hole. A boss is provided on one side of the stainless steel sheath, and the boss has a through hole that passes through the stainless steel sheath. The diameter of the through hole matches the outer diameter of the boss on the plastic connector away from the bottom of the countersunk hole, allowing for coaxial installation. A through hole is provided on the outer surface of the stainless steel sheath, at the same position as the internal threaded hole on the end plate.

[0060] The installation sequence for the endplate connector is as follows: Place the plastic connector into the countersunk hole of the endplate, inserting the boss of the plastic connector facing the countersunk hole into the through hole at the bottom of the countersunk hole, and install a sealing O-ring on the boss. Coaxially install the through hole of the stainless steel sleeve boss onto the outside of the plastic connector, away from the countersunk hole of the endplate. Position the plastic connector and the through hole on the stainless steel sleeve, which is in the same position as the internal threaded hole of the endplate, coaxially. Secure it to the internal threaded hole of the endplate with bolts, completing the positioning and installation of the endplate connector. External piping valves or connectors of the fuel cell stack can be connected to the electrolyte through hole of the plastic connector via piping bonding or heat fusion to allow electrolyte flow.

[0061] Plastic connectors and stainless steel sheathed external piping connections are all completed on the outside of the fuel cell stack endplates, and the assembly sequence is as follows: The end plate of the fuel cell stack is positioned on the fuel cell stacking assembly platform, and the current collector, multiple series-connected single cells, current collector, and end plate are placed on it in sequence to complete the stacking of the fuel cell stack. After the fuel cell stacks are stacked, they can be directly placed into the fuel cell stack press for positioning and clamping, and then the fuel cell stacks can be flipped off the production line.

[0062] After the fuel cell stack is offline, the end plate connector is installed from the outside of the end plate. An O-ring is installed in the O-ring mounting groove on the plastic connector facing the bottom of the countersunk hole on the end plate. The plastic connector is then inserted coaxially into the through hole at the bottom of the countersunk hole on the end plate. Next, a stainless steel sleeve is coaxially installed on the outside of the plastic connector, covering and enclosing the plastic connector facing outwards from the fuel cell stack. Bolts are then passed sequentially through the through holes on the stainless steel sleeve and the plastic connector, corresponding to the internal threaded holes on the end plate, and tightened into the internal threaded holes at the bottom of the countersunk hole on the end plate, completing the positioning and installation.

[0063] Begin testing for internal and external leaks in the fuel cell stack.

[0064] Compared with the existing flow battery stack end plate connector structure, the advantages of the flow battery stack end plate connector proposed in this utility model are as follows: The plastic connector is fitted with a stainless steel sleeve on the outside of the fuel cell stack to provide protection and prevent connector breakage caused by impacts from the inside or outside.

[0065] The sealing O-rings, plastic connectors, and stainless steel sheaths are all installed on the outside of the fuel cell stack. This ensures that there are no protrusions such as connectors on the end plate plane when the fuel cell stack is compressed, and also allows the fuel cell stack to be quickly stacked and taken offline. The automated installation of connectors and internal and external leakage detection are completed offline, which improves the efficiency of fuel cell stack assembly.

[0066] Even if the plastic connector breaks accidentally during subsequent transportation and testing of the fuel cell stack, it is not necessary to disassemble the fuel cell stack for connector repair. The damaged stainless steel sheath, plastic connector, and O-ring can be removed from the outside of the fuel cell stack and replaced with new parts for reinstallation.

[0067] The stainless steel sheath not only protects the plastic joints but also increases their rigidity and enhances the sealing ability of the O-rings. Furthermore, during long-term operation of the fuel cell stack and under alternating high and low temperatures, the stainless steel sheath can reduce the deformation of the plastic joints after experiencing these conditions, thereby reducing or even preventing joint leakage problems caused by long-term operation.

[0068] To further confirm the enhanced protective performance of the proposed flow battery stack endplate connector structure, the most common scenarios for electrolyte inlet and outlet connectors were simulated, including lateral and forward impacts that could cause breakage. At 90° angles to the valves bonded to the inlet and outlet connectors, pendulums made of steel balls weighing 2kg, 5kg, and 8kg were used to strike the connectors of both existing flow battery stacks and stacks using the proposed endplate connector structure. The experimental results showed that under forward impact, the connector of the existing flow battery stack cracked under an 8kg pendulum impact, while the connector of the stack using the proposed endplate connector structure remained undamaged. Under a 90° forward impact, the connector of the existing flow battery stack broke in two under a 5kg pendulum impact, while the connector of the stack using the proposed endplate connector structure cracked under an 8kg pendulum impact. These experiments demonstrate that the proposed flow battery stack endplate connector structure provides enhanced protection against sudden load impacts.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A flow battery stack end plate connector, disposed on the end plate of the stack, characterized in that, The connector includes: Seals are used to prevent electrolyte leakage to the manifold; The connector body is in contact with the electrolyte and mates with the sealing element. The connector body includes a first connecting part and a second connecting part. The first connecting part is used to insert into a preset through hole in the end plate of the fuel cell stack. The first connecting part is provided with a groove to accommodate the sealing element. The second connecting part and the first connecting part are connected by an electrolyte flow channel. The outer periphery of the connector body is provided with a first assembly hole corresponding to the preset threaded hole in the end plate. A rigid protective component is used to protect the connector body and provide rigid support. The rigid protective component is sleeved on the outside of the connector body. The rigid protective component is provided with an adaptation hole that is adapted to the second connecting part. The outer periphery of the rigid protective component is provided with a second assembly hole that corresponds to the position of the first assembly hole. The electrolyte inlet and outlet of the stack end plate are provided with countersunk holes. The bottom of the countersunk holes is provided with a preset through hole adapted to the first connecting part, and the bottom of the countersunk holes is also provided with a preset threaded hole. The connector body is assembled in the countersunk hole, the sealing element is embedded in the groove of the first connecting part, and the rigid protective element is coaxially sleeved on the outside of the second connecting part through the matching hole. The fastener passes through the second assembly hole and the first assembly hole in sequence and then cooperates with the preset threaded hole of the end plate to fix the connector body and the rigid protective element.

2. The flow battery stack end plate connector according to claim 1, characterized in that, The sealing element is a sealing O-ring, the connector body is a plastic connector, and the rigid protective element is a stainless steel sleeve; the sealing O-ring is interference-fitted with the groove of the first connecting part, and the first connecting part of the plastic connector is clearance-fitted with the preset through hole at the bottom of the countersunk hole of the end plate.

3. The flow battery stack end plate connector according to claim 2, characterized in that, The adapter hole of the stainless steel sleeve is clearance-fitted with the second connecting part of the plastic connector, and the inner wall of the stainless steel sleeve is in contact with the outer peripheral surface of the plastic connector.

4. The flow battery stack end plate connector according to claim 2, characterized in that, The end face of the stainless steel sheath away from the adapter hole is flush with the open end face of the countersunk hole on the fuel cell stack end plate. The fastener is a bolt, and the bolt is threadedly connected to the pre-set threaded hole on the end plate.

5. The flow battery stack end plate connector according to claim 1, characterized in that, The diameter of the first connecting part of the connector body is smaller than the diameter of the second connecting part, and the diameter of the adapter hole of the rigid protective component is adapted to the outer diameter of the second connecting part, ensuring that there is no offset when the rigid protective component is sleeved along the axial direction.

6. A flow battery stack, comprising the flow battery stack endplate connector according to any one of claims 1 to 5, characterized in that, It also includes current collectors and single battery packs. The stack end plates are located at both ends of the stack axially. The current collectors are respectively attached to the inner sidewalls of the two stack end plates. The single battery packs are stacked between the two current collectors. After the first connecting part of the connector body of the end plate passes through the preset through hole of the end plate, its end face does not extend beyond the side of the end plate facing the current collector.

7. The flow battery stack according to claim 6, characterized in that, The stack end plate, current collector, and single battery pack are axially fixed by a clamping mechanism. The rigid protective component of the end plate joint does not extend beyond the outer wall of the stack end plate to avoid interference with external structures.

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