Flow battery electrode frame and flow battery stack

Abstract

The invention relates to a flow battery electrode frame and a flow battery stack. The flow battery electrode frame comprises a first end frame, at least one interlayer frame and a second end frame which are stacked in sequence, the flow battery electrode frame is provided with a through electrode cavity, the surfaces, facing the second end frame, of the first end frame and each interlayer frame are provided with a first liquid inlet groove and a first liquid outlet groove, and the surfaces, facing the first end frame, of the second end frame and each interlayer frame are provided with a second liquid inlet groove and a second liquid outlet groove; the adjacent first liquid inlet groove and second liquid inlet groove define a liquid inlet flow channel, the adjacent first liquid outlet groove and second liquid outlet groove define a liquid outlet flow channel, every two adjacent liquid inlet flow channels are connected in series through a liquid inlet communication opening in the interlayer frame, and every two adjacent liquid outlet flow channels are connected in series through a liquid outlet communication opening in the interlayer frame. The liquid inlet flow channel on the first end frame is communicated with the electrode cavity through the liquid inlet and the liquid inlet channel, and the liquid outlet flow channel on the first end frame is communicated with the electrode cavity through the liquid outlet and the liquid outlet channel. The flow battery electrode frame can reduce leakage current.

Description

Technical Field

[0001] The present application relates to the technical field of liquid flow battery energy storage, and in particular to a liquid flow battery electrode frame and a liquid flow battery stack. Background Art

[0002] As a new type of green and environmentally friendly energy storage battery, flow battery has made great progress in recent years and has gradually become the most promising energy storage technology due to its advantages such as deep charge and discharge, low environmental load, high cost performance during the life cycle, no explosion and non-flammability, long service life, scalability, and scrap recycling. The battery stack is the core component of the flow battery system and the main place for chemical reactions to occur, which directly determines the performance and reliability of the system.

[0003] However, as the number of cells in the battery stack increases, the impact of the stack leakage current will gradually be amplified, resulting in limitations in the coulombic efficiency and stability of the battery stack. Generally, extending the flow path of the electrolyte inside the battery stack can effectively suppress the impact of the leakage current. Therefore, how to effectively extend the flow path of the electrolyte becomes the key to suppressing the impact of the leakage current. Summary of the invention

[0004] Based on this, it is necessary to provide a liquid flow battery electrode frame and a liquid flow battery stack to address the above problems. The liquid flow battery electrode frame can suppress the influence of leakage current by extending the flow path of the electrolyte.

[0005] In a first aspect, the present application provides a flow battery electrode frame, comprising a first end frame, at least one interlayer frame and a second end frame stacked in sequence, wherein the flow battery electrode frame is provided with an electrode cavity penetrating the first end frame, the at least one interlayer frame and the second end frame;

[0006] The surface of the first end frame facing the second end frame and the surface of each of the interlayer frames facing the second end frame are both provided with a first liquid inlet groove and a first liquid outlet groove, the surface of the second end frame facing the first end frame and the surface of each of the interlayer frames facing the first end frame are both provided with a second liquid inlet groove and a second liquid outlet groove, the adjacent first liquid inlet grooves and the second liquid inlet grooves are jointly enclosed to form a liquid inlet channel, and the adjacent first liquid outlet grooves and the second liquid outlet grooves are jointly enclosed to form a liquid outlet channel; the liquid inlet channel and the liquid outlet channel are respectively located on both sides of the electrode cavity;

[0007] Each of the interlayer frames is provided with a liquid inlet communication port and a liquid outlet communication port, two adjacent liquid inlet channels are connected in series through the liquid inlet communication port, and two adjacent liquid outlet channels are connected in series through the liquid outlet communication port;

[0008] The first end frame is provided with a liquid inlet and a liquid outlet, and a liquid inlet channel and a liquid outlet channel are provided on the surface of the first end frame facing away from the second end frame, the liquid inlet channel is connected in series with the liquid inlet channel on the first end frame through the liquid inlet, the liquid inlet channel is communicated with one side of the electrode cavity, the liquid outlet channel is connected in series with the liquid outlet channel on the first end frame through the liquid outlet, and the liquid outlet channel is communicated with the other side of the electrode cavity;

[0009] The second end frame is provided with a liquid inlet hole and a liquid outlet hole, the liquid inlet hole is connected with the liquid inlet channel on the second end frame, the liquid inlet hole is used to supply external electrolyte to enter the liquid flow battery electrode frame, the liquid outlet hole is connected with the liquid outlet channel on the second end frame, the liquid outlet hole is used to supply the electrolyte to flow out of the liquid flow battery electrode frame.

[0010] In the above-mentioned liquid flow battery electrode frame, the liquid flow battery electrode frame includes a first end frame, at least one interlayer frame and a second end frame stacked in sequence, the surface of the first end frame facing the second end frame and the surface of each interlayer frame facing the second end frame are both provided with a first liquid inlet groove and a first liquid outlet groove, the surface of the second end frame facing the first end frame and the surface of each interlayer frame facing the first end frame are both provided with a second liquid inlet groove and a second liquid outlet groove, adjacent first liquid inlet grooves and second liquid inlet grooves are jointly enclosed to form a liquid inlet flow channel, adjacent first liquid outlet grooves and second liquid outlet grooves are jointly enclosed to form a liquid outlet flow channel, and multiple The liquid inlet channels are connected in series in sequence and connected to one side of the electrode cavity through the liquid inlet and the liquid inlet channel, and the multiple liquid outlet channels are connected in series in sequence and connected to the other side of the electrode cavity through the liquid outlet and the liquid outlet channel. This allows the external electrolyte to flow into the liquid flow battery electrode frame through the liquid inlet hole. The electrolyte can enter the electrode cavity after flowing through the multiple liquid inlet channels and the liquid inlet channel to undergo an electrochemical reaction with the electrode in the electrode cavity, and the electrolyte after the reaction in the electrode cavity can flow out of the liquid flow battery electrode frame through the liquid outlet hole after flowing through the multiple liquid outlet channels and the liquid outlet channel, so as to ensure the performance of the battery. Among them, since the liquid flow battery electrode frame adopts a multi-layer structure, and each layer is provided with a flow channel structure, so that after the multi-layer structure is assembled, the two adjacent frames can be jointly enclosed to form a liquid inlet flow channel connected in series with the liquid inlet channel and a liquid outlet flow channel connected in series with the liquid outlet channel, so the liquid flow battery electrode frame can effectively extend the total length of the electrolyte flow channel path in the liquid flow battery electrode frame while maintaining the flow resistance of the flow channel, thereby effectively reducing the leakage current, reducing the leakage current effect, and suppressing the influence of the leakage current.

[0011] The technical solution is further described below:

[0012] In one embodiment, the first liquid inlet groove and the second liquid inlet groove each include at least two first connecting grooves and at least one second connecting groove, the at least two first connecting grooves are arranged in an interval, and two adjacent first connecting grooves are connected in series through the second connecting groove;

[0013] And / or, the first liquid outlet groove and the second liquid outlet groove each include at least two third connecting grooves and at least one fourth connecting groove, the at least two third connecting grooves are arranged at intervals, and two adjacent third connecting grooves are connected in series through the fourth connecting groove.

[0014] In one embodiment, the number of the sandwich frames is at least two, and in two adjacent sandwich frames, the liquid inlet communication port of one of the sandwich frames is communicated with one end of the corresponding liquid inlet channel, and the liquid inlet communication port of the other sandwich frame is communicated with the other end of the corresponding liquid inlet channel;

[0015] And / or, the number of the interlayer frames is at least two, and in two adjacent interlayer frames, the liquid outlet connecting port of one of the interlayer frames is connected to one end of the corresponding liquid outlet channel, and the liquid inlet connecting port of the other interlayer frame is connected to the other end of the corresponding liquid outlet channel.

[0016] In one embodiment, the liquid inlet channel and the liquid outlet channel are respectively arranged on two sides of the electrode cavity, and the liquid inlet and the liquid outlet are arranged diagonally on the first end frame.

[0017] In one embodiment, the liquid inlet channel includes a liquid inlet guide channel, a liquid inlet buffer channel and a plurality of liquid inlet distribution channels, the liquid inlet buffer channel is located between the liquid inlet guide channel and the liquid inlet distribution channel, the liquid inlet guide channel connects the liquid inlet port and the liquid inlet buffer channel, each of the liquid inlet distribution channels connects the liquid inlet buffer channel and the electrode cavity, and the plurality of liquid inlet distribution channels are arranged at intervals along the channel width direction of the liquid inlet buffer channel;

[0018] And / or, the liquid outlet channel includes a liquid outlet guide channel, a liquid outlet buffer channel and a plurality of liquid outlet distribution channels, the liquid outlet buffer channel is located between the liquid outlet guide channel and the liquid outlet distribution channel, the liquid outlet guide channel connects the liquid outlet and the liquid outlet buffer channel, each of the liquid outlet buffer channel connects the liquid outlet buffer channel and the electrode cavity, and the plurality of liquid outlet distribution channels are arranged at intervals along the channel width direction of the liquid outlet buffer channel.

[0019] In one embodiment, the first end frame, the at least one interlayer frame and the second end frame are connected as one by welding or bonding in sequence;

[0020] Or, a first mating portion is provided on a surface of the first end frame facing the second end frame and a surface of each interlayer frame facing the second end frame; a second mating portion is provided on a surface of the second end frame facing the first end frame and a surface of each interlayer frame facing the first end frame, and the first mating portion and the second mating portion are detachably sealed and connected.

[0021] In a second aspect, the present application also provides a liquid flow battery stack, comprising any of the liquid flow battery electrode frames described above.

[0022] In the above-mentioned liquid flow battery stack, the liquid flow battery electrode frame includes a first end frame, at least one interlayer frame and a second end frame stacked in sequence, the surface of the first end frame facing the second end frame and the surface of each interlayer frame facing the second end frame are both provided with a first liquid inlet groove and a first liquid outlet groove, the surface of the second end frame facing the first end frame and the surface of each interlayer frame facing the first end frame are both provided with a second liquid inlet groove and a second liquid outlet groove, the adjacent first liquid inlet grooves and the second liquid inlet grooves are jointly enclosed to form a liquid inlet flow channel, the adjacent first liquid outlet grooves and the second liquid outlet grooves are jointly enclosed to form a liquid outlet flow channel, and multiple inlets are provided. The liquid flow channels are connected in series in sequence and connected to one side of the electrode cavity through the liquid inlet and the liquid inlet channel, and the multiple liquid outlet flow channels are connected in series in sequence and connected to the other side of the electrode cavity through the liquid outlet and the liquid outlet channel. This allows the external electrolyte to flow into the liquid flow battery electrode frame through the liquid inlet hole. The electrolyte can enter the electrode cavity after flowing through the multiple liquid inlet flow channels and the liquid inlet channel to undergo an electrochemical reaction with the electrode in the electrode cavity, and the electrolyte after the reaction in the electrode cavity can flow out of the liquid flow battery electrode frame through the liquid outlet hole after flowing through the multiple liquid outlet flow channels and the liquid outlet channel, so as to ensure the performance of the battery. Among them, since the liquid flow battery electrode frame adopts a multi-layer structure, and each layer is provided with a flow channel structure, so that after the multi-layer structure is assembled, the two adjacent frames can jointly enclose a liquid inlet flow channel connected in series with the liquid inlet channel and a liquid outlet flow channel connected in series with the liquid outlet channel. Therefore, the liquid flow battery stack can effectively extend the total length of the electrolyte flow channel path in the liquid flow battery electrode frame while maintaining the flow resistance of the flow channel, thereby effectively reducing the leakage current of the liquid flow battery stack, reducing the leakage current effect, and suppressing the influence of the leakage current.

[0023] In one embodiment, the liquid flow battery stack also includes a first insulating plate and a second insulating plate, the second end frame, the first insulating plate and the second insulating plate are stacked in sequence, and the first insulating plate and the second insulating plate are an integral structure, a first insulating groove is provided on the surface of the first insulating plate facing the second insulating plate, and a second insulating groove is provided on the surface of the second insulating plate facing the first insulating plate, the first insulating groove and the second insulating groove are jointly enclosed to form an insulating flow channel, the first insulating plate is provided with a penetrating connecting hole, one end of the connecting hole is connected to one end of the insulating flow channel, and the other end is connected to the liquid outlet flow channel on the second end frame through the liquid outlet hole, and the other end of the insulating flow channel is used to communicate with an external liquid collecting tank.

[0024] In one embodiment, the first insulating plate and the second insulating plate are connected as one body by welding or bonding.

[0025] In one embodiment, the first insulation groove and the second insulation groove each include at least two first extension grooves and at least one second extension groove, the at least two first extension grooves are arranged at intervals, and two adjacent first extension grooves are connected in series through the second extension groove. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the exploded structure of a liquid flow battery stack in one embodiment.

[0027] Figure 2 for Figure 1 The schematic diagram of the structure of the exploded structure of the flow battery stack shown is shown from another perspective.

[0028] Figure 3 It is a schematic diagram of the front view structure of the sandwich frame in one embodiment.

[0029] Figure 4 It is a schematic diagram of the front view structure of the first end frame in one embodiment.

[0030] Figure 5 It is a schematic diagram of an enlarged structure of a local structure of a first end frame in one embodiment.

[0031] Figure 6 Schematic diagram of the rear structural view of the first insulating plate in one embodiment.

[0032] Description of reference numerals:

[0033] 10. Liquid flow battery stack; 100. Liquid flow battery electrode frame; 101. First liquid inlet; 101a. First connecting groove; 101b. Second connecting groove; 102. First liquid outlet; 102a. Third connecting groove; 102b. Fourth connecting groove; 103. Second liquid inlet; 104. Second liquid outlet; 105. Electrode cavity; 1. First end frame; 11. Liquid inlet; 12. Liquid inlet channel; 121. Liquid inlet guide channel; 122. Liquid inlet buffer channel; 123. Liquid inlet distribution channel ; 13. liquid outlet channel; 131. liquid outlet guide channel; 132. liquid outlet buffer channel; 133. liquid outlet distribution channel; 14. liquid outlet; 2. interlayer frame; 21. liquid inlet connecting port; 22. liquid outlet connecting port; 3. second end frame; 31. liquid inlet hole; 32. liquid outlet hole; 200. first insulating plate; 201. connecting hole; 202. first insulating groove; 202a. first extension groove; 202b. second extension groove; 300. second insulating plate; 301. second insulating groove. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0035] In the description of the present application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0036] In addition, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, if the term "plurality" appears, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0037] In this application, unless otherwise clearly specified and limited, if the terms "installed", "connected", "connected", "fixed" and the like appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0038] In the present application, unless otherwise clearly specified and limited, if there is a description that a first feature is "above" or "below" a second feature, etc., or similar descriptions appear, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0039] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only implementation method.

[0040] See also Figures 1 to 4A liquid flow battery electrode frame 100 provided in an embodiment of the present application comprises a first end frame 1, at least one interlayer frame 2 and a second end frame 3 which are stacked in sequence; the liquid flow battery electrode frame 100 is provided with an electrode cavity 105 which passes through the first end frame 1, at least one interlayer frame 2 and the second end frame 3, and the electrode cavity 105 is used to install electrodes; the surface of the first end frame 1 facing the second end frame 3 and the surface of each interlayer frame 2 facing the second end frame 3 are provided with a first liquid inlet groove 101 and a first liquid outlet groove 102, the surface of the second end frame 3 facing the first end frame 1 and the surface of each interlayer frame 2 facing the first end frame 1 are provided with a second liquid inlet groove 103 and a second liquid outlet groove 104, the adjacent first liquid inlet groove 101 and the second liquid inlet groove 103 are jointly enclosed to form a liquid inlet flow channel, and the adjacent first liquid outlet groove 102 and the second liquid outlet groove 104 are jointly enclosed to form a liquid outlet flow channel; the liquid inlet flow channel and the liquid outlet flow channel are respectively located on both sides of the electrode cavity 105; each interlayer frame 2 is provided with The first end frame 1 is provided with a liquid inlet 11 and a liquid outlet 14, and the surface of the first end frame 1 facing away from the second end frame 3 is provided with a liquid inlet channel 12 and a liquid outlet channel 13, the liquid inlet channel 12 is connected in series with the liquid inlet channel on the first end frame 1 through the liquid inlet 11, and the liquid inlet channel 12 is connected to one side of the electrode cavity 105, and the outlet is connected to the electrode cavity 105. The liquid channel 13 is connected in series with the liquid outlet channel on the first end frame 1 through the liquid outlet 14, and the liquid outlet channel 13 is connected to the other side of the electrode cavity 105; the second end frame 3 is provided with a liquid inlet hole 31 and a liquid outlet hole 32, the liquid inlet hole 31 is connected to the liquid inlet channel on the second end frame 3, the liquid inlet hole 31 is used to supply external electrolyte to enter the liquid flow battery electrode frame 100, the liquid outlet hole 32 is connected to the liquid outlet channel on the second end frame 3, and the liquid outlet hole 32 is used to supply electrolyte to flow out of the liquid flow battery electrode frame 100.

[0041] In the above-mentioned liquid flow battery electrode frame 100, the liquid flow battery electrode frame 100 includes a first end frame 1, at least one interlayer frame 2 and a second end frame 3 stacked in sequence, the surface of the first end frame 1 facing the second end frame 3 and the surface of each interlayer frame 2 facing the second end frame 3 are both provided with a first liquid inlet groove 101 and a first liquid outlet groove 102, the surface of the second end frame 3 facing the first end frame 1 and the surface of each interlayer frame 2 facing the first end frame 1 are both provided with a second liquid inlet groove 103 and a second liquid outlet groove 104, the adjacent first liquid inlet groove 101 and the second liquid inlet groove 103 are jointly enclosed to form a liquid inlet flow channel, the adjacent first liquid outlet groove 102 and the second liquid outlet groove 104 are jointly enclosed to form a liquid outlet flow channel, and After being connected in series, multiple liquid inlet channels are connected to one side of the electrode cavity 105 through the liquid inlet port 11 and the liquid inlet channel 12, and multiple liquid outlet channels are connected to the other side of the electrode cavity 105 through the liquid outlet port 14 and the liquid outlet channel 13. This allows the external electrolyte to flow into the liquid flow battery electrode frame 100 through the liquid inlet hole 31. The electrolyte can enter the electrode cavity 105 after flowing through the multiple liquid inlet channels and the liquid inlet channel 12 to undergo an electrochemical reaction with the electrode in the electrode cavity 105, and the electrolyte after the reaction in the electrode cavity 105 can flow out of the liquid flow battery electrode frame 100 through the liquid outlet hole 32 after flowing through the multiple liquid outlet channels and the liquid outlet channel 13, so as to ensure the performance of the battery. Among them, since the liquid flow battery electrode frame 100 adopts a multi-layer structure, and each layer is provided with a flow channel structure, so that the two adjacent frames after the multi-layer structure is assembled can be enclosed together to form an inlet flow channel connected in series with the inlet channel 12 and an outlet flow channel connected in series with the outlet channel 13, so the liquid flow battery electrode frame 100 can effectively extend the total length of the electrolyte flow channel path in the liquid flow battery electrode frame 100 under the condition of maintaining the flow channel flow resistance, thereby effectively reducing the leakage current, reducing the leakage current effect, and suppressing the influence of the leakage current. In addition, since the two adjacent frames in the liquid flow battery electrode frame 100 can be enclosed together to form an inlet flow channel connected in series with the inlet channel 12 and an outlet flow channel connected in series with the outlet channel 13, when the number of battery stack sections increases, the electrolyte flow channel path can be extended by adjusting the number of interlayer frames 2 to cope with the increase in the leakage current caused by the increase in the number of battery stack sections, and ensure the coulomb efficiency and stability of the battery stack.

[0042] Illustratively, the number of sandwich frames 2 can be adjusted according to actual needs, for example, it can be one, two, three or more. Further, when the number of battery stack nodes increases, the number of sandwich frames 2 can be increased to reduce leakage current.

[0043] Schematically, the liquid inlet hole 31 passes through the second end frame 3, one end of the liquid inlet hole 31 is connected to the liquid inlet channel on the second end frame 3, and the other end is used to communicate with the external liquid storage tank. In this way, the electrolyte stored in the external liquid storage tank can flow into the liquid inlet channel through the liquid inlet hole 31, and after passing through multiple liquid inlet channels and the liquid inlet channel 12, it flows into the electrode cavity 105 to generate an electrochemical reaction with the electrode in the electrode cavity 105.

[0044] Schematically, the liquid outlet hole 32 passes through the second end frame 3, one end of the liquid outlet hole 32 is connected to the liquid outlet channel on the second end frame 3, and the other end is used to communicate with the external liquid collecting tank. In this way, the electrolyte in the electrode cavity 105 that reacts with the electrode can flow out of the flow battery electrode frame 100 through the liquid outlet channel 13, multiple liquid outlet channels and the liquid outlet hole 32, and flow back to the external liquid collecting tank.

[0045] Illustratively, in one embodiment, Figure 1 As shown, the cross-section of the electrode cavity 105 is rectangular; in other embodiments, the cross-section of the electrode cavity 105 may be other shapes, such as circular, triangular, etc.

[0046] Optionally, in one embodiment, Figure 3 As shown, the first liquid inlet 101 and the second liquid inlet 103 each include at least two first connecting grooves 101a and at least one second connecting groove 101b, at least two first connecting grooves 101a are arranged at intervals, and two adjacent first connecting grooves 101a are connected in series through the second connecting groove 101b. In this way, the liquid inlet flow channel formed by the first liquid inlet 101 and the second liquid inlet 103 is in a snake shape, which is conducive to further extending the flow path of the electrolyte when it flows into the electrode cavity 105, thereby helping to further reduce the leakage current, reduce the leakage current effect, and suppress the influence of the leakage current.

[0047] Schematically, the plurality of first connecting grooves 101a are arranged at intervals along the width direction of the interlayer frame 2 or at intervals along the length direction of the interlayer frame 2. Further, the plurality of first connecting grooves 101a are arranged at intervals evenly.

[0048] Schematically, the number of the first connecting grooves 101a and the number of the second connecting grooves 101b can be designed as needed, for example, the number of the first connecting grooves 101a can be three, and the number of the second connecting grooves 101b can be two. Further, when there are multiple second connecting grooves 101b, the two ends of the first connecting groove 101a are respectively connected to the two adjacent second connecting grooves 101b, so that the length of the liquid inlet channel can be effectively guaranteed.

[0049] Illustratively, in one embodiment, the first connecting groove 101a and the second connecting groove 101b are vertically arranged; in other embodiments, the second connecting groove 101b is in an arc shape.

[0050] In other embodiments, the first liquid inlet groove 101 and the second liquid inlet groove 103 may also be linear grooves, so that the liquid inlet channel is linear. For example, the first liquid inlet groove 101 and the second liquid inlet groove 103 both extend along the length direction of the interlayer frame 2 .

[0051] Optionally, in one embodiment, Figure 3 As shown, the first liquid outlet trough 102 and the second liquid outlet trough 104 each include at least two third connecting grooves 102a and at least one fourth connecting groove 102b, at least two third connecting grooves 102a are arranged at intervals, and two adjacent third connecting grooves 102a are connected in series through the fourth connecting groove 102b. In this way, the liquid outlet flow channel formed by the first liquid outlet trough 102 and the second liquid outlet trough 104 is in a snake shape, which is conducive to further extending the flow path of the electrolyte when it flows out of the electrode cavity 105, thereby helping to further reduce the leakage current, reduce the leakage current effect, and suppress the influence of the leakage current.

[0052] Schematically, the plurality of third connecting grooves 102a are arranged at intervals along the width direction of the interlayer frame 2 or at intervals along the length direction of the interlayer frame 2. Further, the plurality of third connecting grooves 102a are arranged at intervals evenly.

[0053] Schematically, the number of the third connecting grooves 102a and the number of the fourth connecting grooves 102b can be designed as needed. For example, the number of the third connecting grooves 102a can be three, and the number of the fourth connecting grooves 102b can be two. Further, when there are multiple third connecting grooves 102a, both ends of the third connecting groove 102a are respectively connected to two adjacent fourth connecting grooves 102b, so that the length of the liquid inlet channel can be effectively guaranteed.

[0054] Illustratively, in one embodiment, the third connecting groove 102a and the fourth connecting groove 102b are vertically arranged; in other embodiments, the fourth connecting groove 102b is in an arc shape.

[0055] In other embodiments, the first liquid outlet groove 102 and the second liquid outlet groove 104 may also be linear grooves, so that the liquid inlet channel is linear. For example, the first liquid outlet groove 102 and the second liquid outlet groove 104 both extend along the length direction of the interlayer frame 2 .

[0056] In one embodiment, the number of the sandwich frames 2 is at least two, and in two adjacent sandwich frames 2, the liquid inlet communication port 21 of one sandwich frame 2 is connected to one end of the corresponding liquid inlet channel, and the liquid inlet communication port 21 of the other sandwich frame 2 is connected to the other end of the corresponding liquid inlet channel. In this way, it can be ensured that the multiple liquid inlet channels in the flow battery electrode frame 100 are connected in series in an end-to-end manner, so that the total flow path of the electrolyte when it flows from the outside into the electrode cavity 105 can be effectively increased, so as to effectively reduce the leakage current, reduce the leakage current effect, and suppress the influence of the leakage current.

[0057] Indicatively, Figure 1 and Figure 2 As shown, one end of the liquid inlet channel on the first end frame 1 is connected to the liquid inlet port 11, and the other end is connected to the liquid inlet communication port 21 opened in the sandwich frame 2 close to the first end frame 1. One end of the liquid inlet channel on the second end frame 3 is connected to the liquid inlet hole 31, and the other end is connected to the liquid inlet communication port 21 opened in the sandwich frame 2 close to the second end frame 3.

[0058] In one embodiment, the number of the sandwich frames 2 is at least two, and in two adjacent sandwich frames 2, the liquid outlet communication port 22 of one sandwich frame 2 is connected to one end of the corresponding liquid outlet flow channel, and the liquid outlet communication port 22 of the other sandwich frame 2 is connected to the other end of the corresponding liquid outlet flow channel. In this way, it can be ensured that the multiple liquid outlet flow channels in the flow battery electrode frame 100 are connected in series in an end-to-end manner, so that the total flow path of the electrolyte when it flows out from the electrode cavity 105 to the outside can be effectively increased, so as to effectively reduce the leakage current, reduce the leakage current effect, and suppress the influence of the leakage current.

[0059] Indicatively, Figure 1 and Figure 2 As shown, one end of the liquid outlet channel on the first end frame 1 is connected to the liquid outlet port 14, and the other end is connected to the liquid outlet communication port 22 opened in the sandwich frame 2 close to the first end frame 1. One end of the liquid outlet channel on the second end frame 3 is connected to the liquid outlet hole 32, and the other end is connected to the liquid outlet communication port 22 opened in the sandwich frame 2 close to the second end frame 3.

[0060] In one embodiment, Figure 1 and Figure 4 As shown, the liquid inlet channel 12 and the liquid outlet channel 13 are respectively arranged on both sides of the electrode cavity 105, and the liquid inlet 11 and the liquid outlet 14 are arranged diagonally on the first end frame 1. In this way, the flow channel for electrolyte to flow into the electrode cavity 105 and the flow channel for electrolyte to flow out of the electrode cavity 105 can be effectively separated on both sides of the electrode cavity 105, thereby improving the stability of the flow battery electrode frame 100.

[0061] In other embodiments, the cross-section of the electrode cavity 105 is rectangular, the liquid inlet channel 12 can be opened on two adjacent frames of the first end frame 1, and the liquid outlet channel 13 is opened on the other two adjacent frames of the first end frame 1.

[0062] Further, in one embodiment, if Figure 4 and Figure 5 As shown, the liquid inlet channel 12 includes a liquid inlet guide channel 121, a liquid inlet buffer channel 122 and a plurality of liquid inlet distribution channels 123. The liquid inlet buffer channel 122 is located between the liquid inlet guide channel 121 and the liquid inlet distribution channel 123. The liquid inlet guide channel 121 connects the liquid inlet port 11 and the liquid inlet buffer channel 122. Each liquid inlet distribution channel 123 connects the liquid inlet buffer channel 122 and the electrode cavity 105. The plurality of liquid inlet distribution channels 123 are arranged at intervals along the channel width direction of the liquid inlet buffer channel 122. In this way, since the multiple liquid inlet distribution channels 123 are arranged at intervals along the channel width direction of the liquid inlet buffer channel 122, when the electrolyte flows from the liquid inlet 11 into the liquid inlet channel 12, the liquid inlet guide channel 121, the liquid inlet buffer channel 122 and the multiple liquid inlet distribution channels 123 can perform secondary distribution on the electrolyte, so that the electrolyte can flow into the electrode cavity 105 more evenly, thereby improving the flow uniformity of the electrolyte in the electrode, reducing the flow resistance of the electrolyte flowing through the electrode, and improving the performance indicators and service life of the liquid flow battery.

[0063] Indicatively, Figure 4 As shown, the flow channel width of the liquid inlet buffer flow channel 122 gradually increases from one end close to the liquid inlet guide channel 121 to the other end. In this way, not only can the liquid inlet guide channel 121, the liquid inlet buffer flow channel 122 and the plurality of liquid inlet distribution flow channels 123 be able to perform secondary distribution on the electrolyte flowing into the electrode cavity 105, but also the pressure at the inlet of the liquid inlet distribution flow channel 123 can be reduced.

[0064] Indicative, combined Figure 5 As shown, a plurality of liquid inlet distribution channels 123 are evenly spaced and arranged along the channel width direction of the liquid inlet buffer channel 122. This is beneficial to further improve the flow uniformity of the electrolyte in the electrode.

[0065] In other embodiments, in combination Figure 4 As shown, the liquid inlet channel 12 may also only include a liquid inlet guide channel 121 and a liquid inlet buffer channel 122. The liquid inlet buffer channel 122 connects the liquid inlet guide channel 121 with the electrode cavity 105. The liquid inlet guide channel 121 is connected with the liquid inlet port 11. The channel width of the liquid inlet buffer channel 122 gradually increases from one end close to the liquid inlet guide channel 121 to the other end.

[0066] Further, in one embodiment, if Figure 4 and Figure 5As shown, the liquid outlet channel 13 includes a liquid outlet guide channel 131, a liquid outlet buffer channel 132 and a plurality of liquid outlet distribution channels 133, the liquid outlet buffer channel 132 is located between the liquid outlet guide channel 131 and the liquid outlet distribution channel 133, the liquid outlet guide channel 131 connects the liquid outlet 14 with the liquid outlet buffer channel 132, each liquid outlet buffer channel 132 connects the liquid outlet buffer channel 132 with the electrode chamber 105, and the plurality of liquid outlet distribution channels 133 are arranged at intervals along the channel width direction of the liquid outlet buffer channel 132. In this way, since the plurality of liquid inlet distribution channels 123 are arranged at intervals along the channel width direction of the liquid inlet buffer channel 122, when the electrolyte after the reaction flows to the liquid outlet side of the electrode chamber 105, the electrolyte can stably and evenly flow out of the electrode chamber 105 to avoid local concentration mutations that affect the stability of the liquid flow battery.

[0067] Indicative, combined Figure 4 As shown, the width of the inlet buffer channel 122 gradually increases from one end close to the inlet guide channel 121 to the other end. In this way, the electrolyte flowing out of the electrode cavity 105 can be accumulated under the guidance of the inlet buffer channel 122 and discharged from the flow battery electrode frame 100 through the outlet channel 13 and the outlet channel.

[0068] Indicative, combined Figure 5 As shown, a plurality of liquid outlet distribution channels 133 are evenly spaced and arranged along the channel width direction of the liquid outlet buffer channel 132. This is beneficial to further improve the flow uniformity of the electrolyte in the electrode.

[0069] In other embodiments, in combination Figure 4 As shown, the liquid outlet channel 13 may also only include a liquid outlet flow channel 131 and a liquid outlet buffer flow channel 132, the liquid outlet buffer flow channel 132 connects the liquid outlet flow channel 131 and the electrode cavity 105, the liquid outlet flow channel 131 is connected to the liquid outlet 14, and the flow channel width of the liquid outlet buffer flow channel 132 gradually increases from one end close to the liquid outlet flow channel 131 to the other end. In this way, the liquid outlet buffer flow channel 132 is directly connected to the electrode cavity 105, which can reduce the pressure loss caused by the local size change of the flow field.

[0070] Optionally, in one embodiment, the first end frame 1, at least one interlayer frame 2 and the second end frame 3 are connected to each other by welding or bonding. In this way, the reliability and stability of the flow battery electrode frame 100 can be effectively guaranteed. At the same time, the sealing performance between two adjacent frames can also be effectively guaranteed.

[0071] Schematically, the first end frame 1, the at least one interlayer frame 2 and the second end frame 3 may be welded and fixed in sequence by laser welding.

[0072] In another embodiment, the surface of the first end frame 1 facing the second end frame 3 and the surface of each interlayer frame 2 facing the second end frame 3 are both provided with a first mating portion; the surface of the second end frame 3 facing the first end frame 1 and the surface of each interlayer frame 2 facing the first end frame 1 are both provided with a second mating portion, and the first mating portion and the second mating portion are detachably sealed and connected. In this way, the number of interlayer frames 2 in the flow battery electrode frame 100 can be adjusted at any time according to the number of battery cells to cope with the increase in leakage current caused by the increase in the number of battery cells. At the same time, the sealing performance between the two adjacent frames can also be effectively guaranteed.

[0073] Optionally, one of the first matching portion and the second matching portion may be a matching groove, and the other may be a matching protrusion, and the matching protrusion may be detachably inserted into the matching groove. In this way, the flow battery electrode frame 100 may be conveniently assembled through the matching groove and the matching protrusion.

[0074] See also Figures 1 to 4 The present application also provides a liquid flow battery stack 10, comprising a liquid flow battery electrode frame 100 according to any of the above embodiments.

[0075] In the above-mentioned liquid flow battery stack 10, the liquid flow battery electrode frame 100 includes a first end frame 1, at least one interlayer frame 2 and a second end frame 3 stacked in sequence, the surface of the first end frame 1 facing the second end frame 3 and the surface of each interlayer frame 2 facing the second end frame 3 are both provided with a first liquid inlet groove 101 and a first liquid outlet groove 102, the surface of the second end frame 3 facing the first end frame 1 and the surface of each interlayer frame 2 facing the first end frame 1 are both provided with a second liquid inlet groove 103 and a second liquid outlet groove 104, the adjacent first liquid inlet groove 101 and the second liquid inlet groove 103 are jointly enclosed to form a liquid inlet flow channel, the adjacent first liquid outlet groove 102 and the second liquid outlet groove 104 are jointly enclosed to form a liquid outlet flow channel, and multiple After the multiple liquid inlet channels are connected in series, they are connected to one side of the electrode cavity 105 through the liquid inlet port 11 and the liquid inlet channel 12, and after the multiple liquid outlet channels are connected in series, they are connected to the other side of the electrode cavity 105 through the liquid outlet port 14 and the liquid outlet channel 13. This allows the external electrolyte to flow into the liquid flow battery electrode frame 100 through the liquid inlet hole 31. The electrolyte can enter the electrode cavity 105 after flowing through the multiple liquid inlet channels and the liquid inlet channel 12 to undergo an electrochemical reaction with the electrode in the electrode cavity 105, and the electrolyte after the reaction in the electrode cavity 105 can flow out of the liquid flow battery electrode frame 100 through the liquid outlet hole 32 after flowing through the multiple liquid outlet channels and the liquid outlet channel 13, so as to ensure the performance of the battery. Among them, since the liquid flow battery electrode frame 100 adopts a multi-layer structure, and each layer is provided with a flow channel structure, so that the two adjacent frames after the multi-layer structure is assembled can be enclosed together to form an inlet flow channel connected in series with the liquid inlet channel 12 and an outlet flow channel connected in series with the liquid outlet channel 13, so the liquid flow battery stack 10 can effectively extend the total length of the electrolyte flow channel path in the liquid flow battery electrode frame 100 under the condition of maintaining the flow channel flow resistance, thereby effectively reducing the leakage current of the liquid flow battery stack 10, reducing the leakage current effect, and suppressing the influence of the leakage current. In addition, since the two adjacent frames in the liquid flow battery electrode frame 100 can be enclosed together to form an inlet flow channel connected in series with the liquid inlet channel 12 and an outlet flow channel connected in series with the liquid outlet channel 13, when the number of battery stack sections increases, the electrolyte flow channel path can be extended by adjusting the number of interlayer frames 2 to cope with the increase in leakage current caused by the increase in the number of battery stack sections, and ensure the coulomb efficiency and stability of the battery stack.

[0076] In one embodiment, Figure 1 and Figure 2As shown, the liquid flow battery stack 10 also includes a first insulating plate 200 and a second insulating plate 300, the second end frame 3, the first insulating plate 200 and the second insulating plate 300 are stacked in sequence, and the first insulating plate 200 and the second insulating plate 300 are an integral structure, a first insulating groove 202 is provided on the surface of the first insulating plate 200 facing the second insulating plate 300, and a second insulating groove 301 is provided on the surface of the second insulating plate 300 facing the first insulating plate 200, the first insulating groove 202 and the second insulating groove 301 are jointly enclosed to form an insulating flow channel, the first insulating plate 200 is provided with a through connecting hole 201, one end of the connecting hole 201 is connected to one end of the insulating flow channel, and the other end is connected to the liquid outlet flow channel on the second end frame 3 through the liquid outlet hole 32, and the other end of the insulating flow channel is used to communicate with an external liquid collecting tank. In this way, the first insulating plate 200 and the second insulating plate 300 connected as one body can realize their insulating function on one side of the liquid flow battery electrode frame 100 to isolate the electrical action between the liquid flow battery electrode frame 100 and other charged structures. In addition, since the first insulating plate 200 and the second insulating plate 300 can form an insulating flow channel, and the insulating flow channel is connected in series with the liquid outlet flow channel on the second end frame 3, so that the electrolyte flowing out of the electrode cavity 105 can flow back to the external liquid collecting tank through the liquid outlet channel 13, multiple liquid outlet flow channels and the insulating flow channel, the design can extend the flow path of the electrolyte flowing out of the liquid flow battery stack 10, thereby effectively reducing the leakage current, reducing the leakage current effect, and suppressing the influence of the leakage current.

[0077] Optionally, in one embodiment, the first insulating plate 200 and the second insulating plate 300 are connected as one body by welding or bonding. In this way, the connection reliability and stability between the first insulating plate 200 and the second insulating plate 300 can be effectively guaranteed. At the same time, the sealing performance between the first insulating plate 200 and the second insulating plate 300 can also be effectively guaranteed.

[0078] Optionally, in one embodiment, Figure 6 As shown, the first insulating groove 202 and the second insulating groove 301 each include at least two first extension grooves 202a and at least one second extension groove 202b, at least two first extension grooves 202a are arranged at intervals, and two adjacent first extension grooves 202a are connected in series through the second extension groove 202b. In this way, the insulating flow channel formed by the first extension groove 202a and the second extension groove 202b is in a snake shape, which can further lengthen the flow path of the electrolyte when it flows out of the electrode cavity 105, thereby helping to further reduce the leakage current, reduce the leakage current effect, and suppress the influence of the leakage current.

[0079] Illustratively, the plurality of first extension grooves 202a are arranged at intervals along the width direction of the first insulating plate 200 or at intervals along the length direction of the first insulating plate 200. Further, the plurality of first extension grooves 202a are arranged at even intervals.

[0080] Schematically, the number of the first extension grooves 202a and the number of the second extension grooves 202b can be designed as needed, for example, the number of the first extension grooves 202a can be six, and the number of the second extension grooves 202b can be five. Furthermore, when there are multiple second extension grooves 202b, both ends of the first extension groove 202a are respectively connected to two adjacent second extension grooves 202b, so that the length of the insulation flow channel can be effectively guaranteed.

[0081] Illustratively, in one embodiment, the first extension groove 202a and the second extension groove 202b are vertically arranged; in other embodiments, the second extension groove 202b is in an arc shape.

[0082] In other embodiments, the first extension groove 202a and the second extension groove 202b may also be linear grooves so that the liquid inlet channel is linear. For example, the first extension groove 202a and the second extension groove 202b both extend along the length direction of the first insulating plate 200 .

[0083] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A liquid flow battery electrode frame, characterized in that: It comprises a first end frame, at least one interlayer frame and a second end frame which are stacked in sequence, wherein the flow battery electrode frame is provided with an electrode cavity which penetrates the first end frame, the at least one interlayer frame and the second end frame; The surface of the first end frame facing the second end frame and the surface of each of the interlayer frames facing the second end frame are both provided with a first liquid inlet groove and a first liquid outlet groove, the surface of the second end frame facing the first end frame and the surface of each of the interlayer frames facing the first end frame are both provided with a second liquid inlet groove and a second liquid outlet groove, the adjacent first liquid inlet grooves and the second liquid inlet grooves are jointly enclosed to form a liquid inlet channel, and the adjacent first liquid outlet grooves and the second liquid outlet grooves are jointly enclosed to form a liquid outlet channel; the liquid inlet channel and the liquid outlet channel are respectively located on both sides of the electrode cavity; Each of the interlayer frames is provided with a liquid inlet communication port and a liquid outlet communication port, two adjacent liquid inlet channels are connected in series through the liquid inlet communication port, and two adjacent liquid outlet channels are connected in series through the liquid outlet communication port; The first end frame is provided with a liquid inlet and a liquid outlet, and a liquid inlet channel and a liquid outlet channel are provided on the surface of the first end frame facing away from the second end frame, the liquid inlet channel is connected in series with the liquid inlet channel on the first end frame through the liquid inlet, the liquid inlet channel is communicated with one side of the electrode cavity, the liquid outlet channel is connected in series with the liquid outlet channel on the first end frame through the liquid outlet, and the liquid outlet channel is communicated with the other side of the electrode cavity; The second end frame is provided with a liquid inlet hole and a liquid outlet hole, the liquid inlet hole is connected with the liquid inlet channel on the second end frame, the liquid inlet hole is used to supply external electrolyte to enter the liquid flow battery electrode frame, the liquid outlet hole is connected with the liquid outlet channel on the second end frame, the liquid outlet hole is used to supply the electrolyte to flow out of the liquid flow battery electrode frame.

2. The flow battery electrode frame according to claim 1, characterized in that: The first liquid inlet groove and the second liquid inlet groove each include at least two first connecting grooves and at least one second connecting groove, the at least two first connecting grooves are arranged in an interval, and two adjacent first connecting grooves are connected in series through the second connecting groove; And / or, the first liquid outlet groove and the second liquid outlet groove each include at least two third connecting grooves and at least one fourth connecting groove, the at least two third connecting grooves are arranged at intervals, and two adjacent third connecting grooves are connected in series through the fourth connecting groove.

3. The flow battery electrode frame according to claim 1, characterized in that: There are at least two interlayer frames, and in two adjacent interlayer frames, the liquid inlet communication port of one interlayer frame is communicated with one end of the corresponding liquid inlet channel, and the liquid inlet communication port of the other interlayer frame is communicated with the other end of the corresponding liquid inlet channel; And / or, the number of the interlayer frames is at least two, and in two adjacent interlayer frames, the liquid outlet connecting port of one of the interlayer frames is connected to one end of the corresponding liquid outlet channel, and the liquid inlet connecting port of the other interlayer frame is connected to the other end of the corresponding liquid outlet channel.

4. The flow battery electrode frame according to claim 1, characterized in that: The liquid inlet channel and the liquid outlet channel are respectively arranged on both sides of the electrode cavity, and the liquid inlet and the liquid outlet are arranged diagonally on the first end frame.

5. The flow battery electrode frame according to claim 4, characterized in that: The liquid inlet channel includes a liquid inlet guide channel, a liquid inlet buffer channel and a plurality of liquid inlet distribution channels, wherein the liquid inlet buffer channel is located between the liquid inlet guide channel and the liquid inlet distribution channel, the liquid inlet guide channel connects the liquid inlet port and the liquid inlet buffer channel, each of the liquid inlet distribution channels connects the liquid inlet buffer channel and the electrode cavity, and the plurality of liquid inlet distribution channels are arranged at intervals along the channel width direction of the liquid inlet buffer channel; And / or, the liquid outlet channel includes a liquid outlet guide channel, a liquid outlet buffer channel and a plurality of liquid outlet distribution channels, the liquid outlet buffer channel is located between the liquid outlet guide channel and the liquid outlet distribution channel, the liquid outlet guide channel connects the liquid outlet and the liquid outlet buffer channel, each of the liquid outlet buffer channel connects the liquid outlet buffer channel and the electrode cavity, and the plurality of liquid outlet distribution channels are arranged at intervals along the channel width direction of the liquid outlet buffer channel.

6. The flow battery electrode frame according to claim 1, characterized in that: The first end frame, the at least one interlayer frame and the second end frame are connected as one by welding or bonding in sequence; Or, a first mating portion is provided on a surface of the first end frame facing the second end frame and a surface of each interlayer frame facing the second end frame; a second mating portion is provided on a surface of the second end frame facing the first end frame and a surface of each interlayer frame facing the first end frame, and the first mating portion and the second mating portion are detachably sealed and connected.

7. A liquid flow battery stack, characterized in that: A liquid flow battery electrode frame comprising any one of claims 1 to 6.

8. The flow battery stack according to claim 7, characterized in that: The liquid flow battery stack also includes a first insulating plate and a second insulating plate. The second end frame, the first insulating plate and the second insulating plate are stacked in sequence, and the first insulating plate and the second insulating plate are an integral structure. A first insulating groove is provided on the surface of the first insulating plate facing the second insulating plate, and a second insulating groove is provided on the surface of the second insulating plate facing the first insulating plate. The first insulating groove and the second insulating groove are jointly enclosed to form an insulating flow channel. The first insulating plate is provided with a penetrating connecting hole, one end of the connecting hole is connected to one end of the insulating flow channel, and the other end is connected to the liquid outlet flow channel on the second end frame through the liquid outlet hole. The other end of the insulating flow channel is used to communicate with an external liquid collecting tank.

9. The flow battery stack according to claim 8, characterized in that: The first insulating plate and the second insulating plate are connected as a whole by welding or bonding.

10. The flow battery stack according to claim 8, characterized in that: The first insulation groove and the second insulation groove each include at least two first extension grooves and at least one second extension groove, the at least two first extension grooves are arranged at intervals, and two adjacent first extension grooves are connected in series through the second extension groove.

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