Iron-chromium redox flow battery bipolar plate and flow battery

Abstract

The utility model relates to an iron-chromium redox flow battery bipolar plate and a flow battery, the bipolar plate comprises a bipolar plate body, the bipolar plate body is provided with an electrolyte inlet for an electrolyte of the flow battery to enter and an electrolyte outlet for the electrolyte of the flow battery to flow out, a flow channel is arranged between the electrolyte inlet and the electrolyte outlet and comprises a plurality of branch channels; and a plurality of reducing structures are arranged on the pipe walls of the branch channels. According to the scheme, the electrolyte solution is mixed more uniformly, the contact area between the electrolyte solution and the electrode is increased, the electrolyte in the flow channel seeps into the electrode as much as possible to participate in electrochemical reaction, the reaction is more sufficient and complete, and the efficiency of the battery system is relatively high.

Description

Technical Field

[0001] The present application belongs to the technical field of liquid flow batteries, and specifically, relates to an iron-chromium redox liquid flow battery bipolar plate and a liquid flow battery thereof. Background Art

[0002] Energy storage technology can effectively regulate the instability of renewable energy generation and achieve safe and stable power supply. Therefore, energy storage technology is a key supporting technology for building a new power system with new energy as the main body and achieving dual carbon goals. Among the many energy storage technologies, liquid flow battery energy storage technology realizes the mutual conversion of electrical energy and chemical energy through the redox reaction of active substances in the electrolyte on the electrode. It has the advantages of high safety, long life, and environmental friendliness, and has received widespread attention. Among them, iron-chromium liquid flow battery energy storage technology is expected to be widely used in energy storage technology due to its advantages such as low raw material cost, low environmental harm, and wide operating temperature range. In the prior art, the flow mode of the electrolyte in the bipolar plate flow channel of the common iron-chromium liquid flow battery has problems such as large liquid flow resistance, high energy consumption, uneven electrolyte distribution, severe polarization, and low battery system efficiency. The present invention comes from this. Summary of the invention

[0003] The embodiment of the present application provides a bipolar plate for an iron-chromium redox flow battery, which can achieve a full reaction of the iron-chromium redox flow battery, and the efficiency of the battery system is relatively high.

[0004] In a first aspect, an embodiment of the present application provides an iron-chromium redox flow battery bipolar plate, comprising:

[0005] A bipolar plate body, wherein the bipolar plate body is provided with an electrolyte inlet for the electrolyte of the liquid flow battery to enter and an electrolyte outlet for the electrolyte of the liquid flow battery to flow out, a flow channel is provided between the electrolyte inlet and the electrolyte outlet, and the flow channel includes a plurality of branch channels;

[0006] A plurality of diameter-changing structures are arranged on the tube wall of the branch channel.

[0007] In some possible embodiments, the variable diameter structure is beaded, and the orthographic projection of the variable diameter structure on the bipolar plate body is a symmetrical figure along the first direction and the second direction; the first direction is the flow direction of the electrolyte in the branch channel; the second direction is a direction perpendicular to the flow direction of the electrolyte in the branch channel;

[0008] The diameter-changing structures are arranged in an array along the flow direction of the electrolyte in the branch channel, and the intervals between adjacent diameter-changing structures are equal or unequal.

[0009] In some possible embodiments, the variable diameter structure includes two or more single bead structures arranged in sequence along the flow direction of the electrolyte in the branch channel, and the orthographic projection pattern of the single bead structure on the bipolar plate body is mirror-symmetrical in the second direction;

[0010] The orthographic projection shape of the single bead structure on the bipolar plate body is two mirror-symmetrical arcs, a fan, a cone, or a polygon.

[0011] In some possible embodiments, the diameter-varying structure has a virtual center line along the flow direction of the electrolyte in the branch channel that is perpendicular to the flow direction of the electrolyte in the branch channel, and the diameter-varying structure is mirror-symmetrical on both sides of the virtual center line.

[0012] In some possible embodiments, the variable diameter structure includes a first single-bead structure and a second single-bead structure, and the first single-bead structure and the second single-bead structure are connected in series in sequence along the flow direction of the electrolyte in the branch channel; there is a first spacing between the first single-bead structure and the second single-bead structure; there is a second spacing between adjacent variable diameter structures; the first spacing is smaller than the second spacing; and the first spacing is zero.

[0013] In some possible embodiments, the first single-bead structure and the second single-bead structure are symmetrically arranged along the flow direction of the electrolyte in the branch channel; and a third single-bead structure is arranged between the first single-bead structure and the second single-bead structure.

[0014] In some possible embodiments, the third single-bead structure, the first single-bead structure and the second single-bead structure have the same shape, and the orthographic projection figures of the single-bead structure on the bipolar plate body are symmetrical figures along the first direction and the second direction;

[0015] The single bead structure forms a virtual circle or hexagon in the orthographic projection of the bipolar plate body.

[0016] In some possible embodiments, the orthographic projection pattern of the first single-bead structure on the bipolar plate body and the orthographic projection pattern of the second single-bead structure on the bipolar plate body are mirror-symmetric in the first direction, and the orthographic projection pattern of the third single-bead structure on the bipolar plate body is different from the orthographic projection pattern of the second single-bead structure on the bipolar plate body.

[0017] In some possible embodiments, the flow channel includes a liquid inlet channel, a liquid outlet channel, and a serpentine flow channel arranged between the liquid inlet channel and the liquid outlet channel, the serpentine flow channel includes an elbow portion and a branch channel, and the branch channel is arranged between two adjacent elbow portions or between the elbow portion and the liquid inlet channel, and between the elbow portion and the liquid outlet channel;

[0018] Alternatively, the flow channel includes a liquid inlet channel, a liquid outlet channel, and an interdigitated flow channel arranged between the liquid inlet channel and the liquid outlet channel; the interdigitated flow channel includes a distribution flow channel and a branch channel connected to the distribution flow channel.

[0019] A second aspect of the present invention provides an iron-chromium redox flow battery, which includes the above-mentioned iron-chromium redox flow battery bipolar plate.

[0020] The present application provides an iron-chromium redox flow battery bipolar plate. By designing a plurality of variable diameter structures in the flow channel of the iron-chromium redox flow battery bipolar plate, the electrolyte solution is mixed more evenly, the contact area between the electrolyte solution and the electrode is increased, and the electrolyte in the flow channel is allowed to seep into the electrode as much as possible to participate in the electrochemical reaction, so that the reaction is more sufficient and complete, and the efficiency of the battery system is relatively high. Moreover, the orthographic projection figure of the variable diameter structure on the bipolar plate body is a symmetrical figure along the first direction and the second direction. This design makes the electrolyte fluid in the flow channel present periodic pressure changes, increases the length of the flow path of the electrolyte solution on the bipolar plate, improves the performance of the flow battery, and extends the service life of the flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0022] Figure 1 A schematic diagram of the channel structure of a bipolar plate of an iron-chromium redox flow battery in the prior art;

[0023] Figure 2 A schematic diagram of the structure of a bipolar plate for an iron-chromium redox flow battery provided in an embodiment of the present application;

[0024] Figure 3 for Figure 2 A schematic diagram of the enlarged structure at point A;

[0025] Figure 4 for Figure 2 Another enlarged structural diagram at A;

[0026] Figure 5 A schematic diagram of the structure of a bipolar plate for an iron-chromium redox flow battery provided in yet another embodiment of the present application;

[0027] Figure 6 for Figure 5 Schematic diagram of the enlarged structure at B.

[0028] Figure 7This is a schematic structural diagram of a bipolar plate for an iron-chromium redox flow battery according to another embodiment of the present invention.

[0029] Figure 8 This is a schematic structural diagram of a bipolar plate for an iron-chromium redox flow battery according to another embodiment of the present invention.

[0030] Fig. 9 This is a schematic structural diagram of a bipolar plate for an iron-chromium redox flow battery according to another embodiment of the present invention.

[0031] Fig.10 This is a schematic structural diagram of a bipolar plate for an iron-chromium redox flow battery according to another embodiment of the present invention.

[0032] Fig.11 This is a schematic structural diagram of a bipolar plate for an iron-chromium redox flow battery according to another embodiment of the present invention.

[0033] Fig.12 It is a schematic diagram of the structure of an iron-chromium redox flow battery stack according to an embodiment of the present invention.

[0034] In the figure: 1-first end plate; 2-first bipolar plate; 3-positive electrode frame; 4-positive terminal; 5-proton membrane; 6-negative terminal; 7-negative electrode frame; 8-second bipolar plate; 9-second end plate;

[0035] 21-bipolar plate body; 22-electrolyte inlet; 23-electrolyte outlet; 24-elevation head; 25-branch channel; 26-diameter reducing structure; 27-flow channel; 28-middle active area; 29-distribution flow channel;

[0036] 261-first single bead structure; 262-second single bead structure; 263-third single bead structure; 264-narrow flow area; 265-wide flow area; 221-liquid inlet channel; 231-liquid outlet channel. Y-first direction; X is the second direction. DETAILED DESCRIPTION

[0037] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by illustrating the examples of the present application.

[0038] It should be understood that in the description of the specification and claims of this application, if there are terms such as "first", "second", etc., they are only used to distinguish the objects described, and do not have any order or technical meaning. Therefore, the objects defined as "first", "second", etc. may explicitly or implicitly include one or more of the objects. In addition, "one" or "a" and similar words do not indicate a quantitative limitation, but indicate the existence of at least one, and "multiple" means no less than two.

[0039] In the description of the specification and claims of this application, if there are terms such as "upper", "lower", "horizontal" and the like indicating an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, it is only for the convenience of describing the application clearly and simply, and does not indicate or imply that the elements referred to must have a specific direction, be constructed and operated in a specific orientation. These directional terms are relative concepts, used for relative description and clarification, and may change accordingly according to the change in the orientation of the components in the drawings. For example, if the device in the figure is turned over, the elements described as "below" other elements will be positioned "above" other elements.

[0040] In the prior art, liquid flow batteries are a type of electrochemical energy storage technology, which generally utilizes the changes in the valence state of active substances in the positive and negative liquid phases during the charging and discharging process to achieve energy storage and release. Liquid flow batteries include technologies such as all-vanadium liquid flow batteries, iron-chromium liquid flow batteries, and zinc-bromine liquid flow batteries. Liquid flow batteries have independent energy units and power units. The energy unit generally refers to the positive and negative electrolytes of the battery. The concentration and volume of the active substances in the electrolyte determine the energy upper limit of the liquid flow battery. The power unit generally refers to a single cell or a battery stack. The electrolyte flows through the electrodes in the battery stack, and the active substances react on the surface of the electrodes, thereby converting chemical energy into electrical energy, or converting electrical energy into chemical energy.

[0041] The battery stack of a flow battery is mainly composed of electrodes, diaphragms, bipolar plates, current collectors, etc. Among them, the bipolar plate is one of the key components of a flow battery. It connects the positive and negative electrodes of different cells and conducts the internal circuit of the battery. It should have good electrical conductivity, mechanical strength, and resistance to chemical oxidation and electrochemical corrosion. Figure 1 The figure shows a typical bipolar plate flow channel structure in the prior art. The present invention provides a method for designing a bipolar plate surface flow channel for an iron-chromium redox flow battery, so that the flow battery has a higher power density and can reduce the pressure drop.

[0042] like Figure 2As shown, it is a schematic diagram of the structure of the bipolar plate of the iron-chromium redox flow battery of the embodiment of the present invention; it comprises: a bipolar plate body 21, the bipolar plate body 21 is provided with an electrolyte inlet 22 for the electrolyte of the flow battery to enter and an electrolyte outlet 23 for the electrolyte of the flow battery to flow out, a flow channel 27 is arranged between the electrolyte inlet 22 and the electrolyte outlet 23, and the flow channel 27 comprises a plurality of branch channels 25; a plurality of diameter-changing structures 26 are arranged on the tube wall of the branch channel 25. The diameter-changing structure 26 of the present invention has a narrow flow area 264 and a wide flow area 265; wherein the cross-sectional area of ​​the narrow flow area 264 is smaller than the cross-sectional area of ​​the wide flow area 265, wherein the cross-sectional area of ​​the narrow flow area 264 can be defined as a cross-sectional area perpendicular to the flow direction of the electrolyte when the electrolyte flows through the narrow flow area 264; the cross-sectional area of ​​the wide flow area 265 can be defined as a cross-sectional area perpendicular to the flow direction of the electrolyte when the electrolyte flows through the wide flow area 265. By providing the variable diameter structure 26, the electrolyte solution forms a reflux when passing through the narrow flow area 264 and the wide flow area 265 during the flow process, which promotes the mixing of the electrolyte solution to achieve uniform distribution of the electrolyte, and also increases the contact area between the electrolyte solution and the electrode.

[0043] In a preferred embodiment of the present invention, Figure 3 and Figure 4 As shown, the variable diameter structure 26 is beaded, and the orthographic projection of the variable diameter structure 26 on the bipolar plate body 21 is a symmetrical figure along the first direction and the second direction; the first direction Y is the flow direction of the electrolyte in the branch channel 25; the second direction X is the direction perpendicular to the flow direction of the electrolyte in the branch channel 25; the variable diameter structure 26 is arranged in an array along the flow direction of the electrolyte in the branch channel 25, and the spacing between adjacent variable diameter structures 26 is equal or unequal. By setting the beaded variable diameter structure 26, the electrolyte solution forms a continuous reciprocating turbulent flow in the bipolar plate flow channel, so that the electrolyte is quickly and evenly distributed in the area where the variable diameter structure 26 is located, and the deposition of the internal electrolyte solution can be avoided. Since the electrolyte solution flows alternately in the flow channel 27, it continuously turns in different directions, thereby promoting the mixing of various components in the electrolyte solution.

[0044] In a preferred embodiment of the present invention, the variable diameter structure 26 includes two or more single bead structures arranged in sequence along the flow direction of the electrolyte in the branch channel 25, and the orthographic projection pattern of the single bead structure on the bipolar plate body 21 is mirror-symmetrical in the second direction; Figure 5 , Figure 6 , Figure 7 , Figure 8 and Fig. 9As shown, the orthographic projection of the single bead structure on the bipolar plate body 21 is a mirror-symmetrical arc, fan, cone, or polygon. The fluids formed on both sides of the branch channel 25 of the flow channel 27 have roughly the same shape, which can accelerate the mixing of various components in the electrolyte solution.

[0045] In a preferred embodiment of the present invention, the variable diameter structure 26 has a virtual center line perpendicular to the flow direction of the electrolyte in the branch channel 25 along the flow direction of the electrolyte in the branch channel 25, and the variable diameter structure 26 is mirror-symmetrical on both sides of the virtual center line. The variable diameter structure 26 is arranged in a mirror-symmetrical manner on both sides of the virtual center line, which can stabilize the turbulence formed by the electrolyte solution fluid, facilitate the mixing of the fluid in the branch channel 25 of the non-variable diameter structure 26, and enable the electrolyte in the branch channel 25 of the non-variable diameter structure 26 to infiltrate into the electrode as much as possible to participate in the electrochemical reaction.

[0046] In a preferred embodiment of the present invention, Figure 2 and Figure 3 as well as Figure 4 As shown, the variable diameter structure 26 includes a first single bead structure 261 and a second single bead structure 262, and the first single bead structure 261 and the second single bead structure 262 are sequentially connected in series along the flow direction of the electrolyte in the branch channel 25; there is a first spacing D1 between the first single bead structure 261 and the second single bead structure 262; there is a second spacing D2 between adjacent variable diameter structures 26; the first spacing D1 is smaller than the second spacing D2; the first spacing D1 is zero. The second spacing D2 can be 6mm-8mm; the first spacing D1 can be 0mm-8mm. By adjusting the size of the first spacing and the second spacing, the electrolyte in the branch channel 25 of the variable diameter structure 26 and the non-variable diameter structure 26 can be adjusted to flow into the electrode as much as possible to participate in the electrochemical reaction, so as to meet the service life and performance requirements of different liquid flow batteries.

[0047] In a preferred embodiment of the present invention, Figure 3 , Figure 4 As shown, the first single bead structure 261 and the second single bead structure 262 are symmetrically arranged along the flow direction of the electrolyte in the branch channel 25; Figure 5 and Figure 6 As shown, a third single bead structure 263 is disposed between the first single bead structure 261 and the second single bead structure 262. By providing more than two single bead structures and providing periodically alternating variable diameter structures 26, the length of the flow path of the electrolyte solution in the bipolar plate flow channel is increased, and the fluid mixing effect of the branch channel 25 is enhanced.

[0048] In a preferred embodiment of the present invention, Figure 5 and Figure 6As shown, the third single bead structure 263, the first single bead structure 261 and the second single bead structure 262 have the same shape, and the orthographic projection figures of the single bead structure on the bipolar plate body 21 are symmetrical figures along the first direction and the second direction; the orthographic projection figures of the single bead structure on the bipolar plate body 21 form a virtual circle or hexagon. The present invention not only enhances the turbulent mixing effect through the periodically alternating variable diameter structure 26, but also makes the electrolyte solution on both sides turbulently mixed through the symmetrical design, meeting the performance requirements of a stronger liquid flow battery.

[0049] In a preferred embodiment of the present invention, Figure 6 As shown, the orthographic projection figure of the first single bead structure 261 on the bipolar plate body 21 and the orthographic projection figure of the second single bead structure 262 on the bipolar plate body 21 are mirror-symmetric in the first direction, and the orthographic projection figure of the third single bead structure 263 on the bipolar plate body 21 is different from the orthographic projection figure of the second single bead structure 262 on the bipolar plate body 21. By setting different periodic structures, different turbulent mixing effects can be achieved, so that the turbulent mixing effects of the electrolyte solution are different, which can meet the different performance requirements and service life of the liquid flow battery, and can also control different manufacturing and processing costs.

[0050] In a preferred embodiment of the present invention, Figure 2 to Figure 10 As shown, the flow channel 27 includes an inlet channel 221, an outlet channel 231, and a serpentine flow channel arranged between the inlet channel 221 and the outlet channel 231. The serpentine flow channel includes an elbow portion 24 and a branch channel 25. The branch channel 25 is arranged between two adjacent elbow portions 24 or between the elbow portion 24 and the inlet channel 221, and between the elbow portion 24 and the outlet channel 231. The flow channel 27 includes: an inlet channel 221, a serpentine flow channel including a plurality of elbow portions 24, and an outlet channel 231, which are used to form an electrolyte transport channel together; the inlet channel 221, the serpentine flow channel, and the outlet channel 231 are provided with at least one variable diameter structure 26 at intervals along the flow channel wall in the electrolyte flow direction; the number of the variable diameter structures 26 in the flow channel in the vertical direction of the electrolyte flow is 3-10. By providing different numbers of variable diameter structures 26 , the overall length of the serpentine flow channel is increased, thereby increasing the length of the flow path of the electrolyte solution in the bipolar plate flow channel and enhancing the fluid mixing effect of its branch channel 25 .

[0051] In a preferred embodiment of the present invention, one end of the liquid inlet channel is connected to the electrolyte inlet 22, and the other end is connected to the elbow 24 through a branch channel 25; the serpentine flow channel is distributed in a serpentine shape and the branch channels 25 are connected in sequence, wherein the branch channels 25 and the adjacent elbows 24 are connected and vertically connected; one end of the liquid outlet channel 231 is connected to the elbow 24 through the branch channel 25, and the other end is connected to the electrolyte outlet 23. The branch channel 25 is located in the active area in the middle of the positive and negative electrodes.

[0052] In a preferred embodiment of the present invention, the bipolar plate body is a non-porous graphite plate, and the thickness of the non-porous graphite plate is 4mm, and the area size is 2.1cm×2.1cm. The maximum width of the narrow flow area 264 of the variable diameter structure 26 is the same as the inflow width of the wide flow area 265; the maximum width of the narrow flow area 264 of the variable diameter structure 26 and the inflow width of the wide flow area 265 of the variable diameter structure 26 are 2-4mm, specifically, 2mm, 3mm or 4mm; the maximum width of the wide flow area 265 of the variable diameter structure 26 is 6mm-8mm, specifically, 6mm, 7mm or 8mm.

[0053] The single column structure inside the variable diameter structure 26 is arranged at equal intervals periodically, and the second interval between adjacent variable diameter structures 26 can be adjusted according to actual conditions. In a preferred embodiment of the present invention, the electrolyte inlet 22 is vertically arranged at the liquid inlet channel 221, the liquid inlet channel 221 is vertical to the branch channel 25, and the liquid outlet channel 231 is vertical to the electrolyte outlet 23. The present invention has a simple structure, is easy to process and has low cost.

[0054] In a preferred embodiment of the present invention, Fig.11 As shown, the variable diameter structure 26 of the present invention can also be applied to non-serpentine flow channels, such as interdigitated flow channels. Figure 7 As shown, the flow channel includes an inlet channel 221, an outlet channel 231 and a forked-finger flow channel arranged between the inlet channel 221 and the outlet channel 231; the forked-finger flow channel includes a distribution channel 29 and a branch channel 25 connected to the distribution channel 29. The positive projection of each single-bead structure in the variable diameter structure on the bipolar plate body can be a virtual regular hexagon. The variable diameter structure 26 is in the shape of a string of beads, and the single-bead structure is in the shape of a honeycomb, and its positive projection on the bipolar plate body 21 is a hexagon. The specific variable diameter structure 26 of the embodiment of this case can be formed by two single-bead structures cascaded in sequence, or it can be formed by three single-bead structures cascaded in sequence.

[0055] In this embodiment, the variable diameter structure 26 includes a narrow flow area and a wide flow area; wherein the cross-sectional area of ​​the narrow flow area is smaller than the cross-sectional area of ​​the wide flow area; the maximum width L3 of the narrow flow area of ​​the variable diameter structure 26 is 2-4 mm, specifically, it can be 2 mm, 3 mm or 4 mm. The orthographic projection figure of the wide flow area on the bipolar plate body is a regular hexagon formed by symmetrical polygons. The side length of the regular hexagon and the maximum width L3 of the narrow flow area of ​​the variable diameter structure 26 are 2-4 mm.

[0056] like Fig.11 As shown, in this embodiment, the width of the branch channel 25 is equal to the side length of the regular hexagon of the single bead structure projection of the variable diameter structure 26. In the vertical direction, the cross-sectional area of ​​the branch channel 25 is 24mm2; and the maximum cross-sectional area of ​​the variable diameter structure 26 is 48mm2. The advantage of this design is that when the electrolyte flows from the branch channel 25 into the variable diameter structure 26, due to the larger cross-sectional area, the electrolyte flowing through will be backflowed, causing secondary mixing of the electrolyte, making the electrolyte mixing more uniform. At the same time, designing the branch channel 25 of the electrolyte into the variable diameter structure 26 can increase the contact area between the electrolyte and the electrode, and in the electrolyte transportation of a single cycle, as much electrolyte as possible can be allowed to seep into the electrode to participate in the electrochemical reaction.

[0057] The following is a detailed description of different channel forms.

[0058] In a preferred embodiment of the present invention, Figure 2 to Figure 10 As shown, the iron-chromium redox flow battery of the present invention includes an iron-chromium redox flow battery bipolar plate. Taking the positive electrode side as an example, the iron-chromium redox flow battery bipolar plate includes a bipolar plate body; the bipolar plate body includes: a flow channel, a positive electrode electrolyte inlet 22 located on the flow channel, and a positive electrode electrolyte outlet 23;

[0059] In this embodiment, the flow channel includes: a positive electrode liquid inlet channel 221, a positive electrode serpentine flow channel including a plurality of elbows 24, and a positive electrode liquid outlet channel 231, which are used to jointly form an electrolyte transport channel; wherein the positive electrode electrolyte inlet 22 is connected to the positive electrode liquid inlet channel 221; the positive electrode serpentine flow channel is connected to the positive electrode liquid inlet channel 221, the positive electrode serpentine flow channel also includes a plurality of elbows 24, and the liquid outlet channel 231 is connected to the positive electrode serpentine flow channel, and is connected to the positive electrode electrolyte outlet 23.

[0060] The positive electrode serpentine flow channel is distributed in a serpentine shape and interconnected, and is located in the active area in the middle of the positive electrode side. The branch channel 25 of the positive electrode serpentine flow channel is perpendicular to the elbow 24.

[0061] The electrolyte flows into the positive electrode inlet channel 221 from the positive electrode electrolyte inlet 22. The electrolyte enters the electrode through the positive electrode serpentine flow channel, completes the electrochemical reaction, and then flows directly into the positive electrode serpentine flow channel. The electrolyte in the positive electrode serpentine flow channel flows into the positive electrode outlet channel 231, passes through the positive electrode outlet channel 231 and is discharged from the positive electrode electrolyte outlet 23, completing the flow process of the electrolyte in the battery.

[0062] The active areas on both sides of the bipolar plate are consistent, the serpentine flow channels on the positive electrode inlet side are consistent with the serpentine flow channels on the negative electrode inlet side, the positive electrode inlet flow channels are consistent with the negative electrode inlet flow channels, and the positive electrode outlet flow channels are consistent with the negative electrode outlet flow channels.

[0063] The positive electrode liquid inlet channel 221, the positive electrode serpentine channel and the positive electrode liquid outlet channel 231 are provided with at least one variable diameter structure 26 at intervals along the flow direction of the electrolyte; the number of the variable diameter structures 26 along the vertical direction of the electrolyte flow is shown as 4 or 5, and can be more.

[0064] The positive electrode serpentine flow channel is distributed in a serpentine shape and the branch channels 25 are connected in sequence. The branch channels 25 and the adjacent elbows 24 are perpendicular to each other. The branch channels 25 are located in the active area 28 in the middle of the positive electrode. One end of the positive electrode liquid outlet channel 231 is connected to the elbow 24, and the other end is connected to the positive electrode electrolyte outlet 23. In the embodiment of the present invention, the bipolar plate body is a non-porous graphite plate, and the thickness of the non-porous graphite plate is 4 mm, and the area size is 2.1 cm×2.1 cm.

[0065] In this embodiment, the variable diameter structure 26 of the positive electrode liquid inlet channel 221, the positive electrode serpentine flow channel and the positive electrode liquid outlet channel 231 includes a narrow flow area 264 and a wide flow area 265; wherein the cross-sectional area of ​​the narrow flow area 264 is smaller than the cross-sectional area of ​​the wide flow area 265; the maximum width L3 of the narrow flow area 264 of the variable diameter structure 26 is 2-4 mm, specifically, it can be 2 mm, 3 mm or 4 mm.

[0066] It should be noted that the flow channel of the variable diameter structure 26 is arranged parallel to the membrane plane and is seamlessly fitted with the electrode. After the electrolyte solution is pumped in by the power circulation pump, it flows through the positive electrode electrolyte inlet 22 through the positive electrode liquid inlet channel 221, and then flows from the positive electrode liquid inlet channel 221 through the elbow 24 into the positive electrode serpentine flow channel. The electrolyte solution enters the electrode through the positive electrode serpentine flow channel to complete the electrochemical reaction, and then flows directly into the positive electrode serpentine flow channel. The electrolyte in the positive electrode serpentine flow channel flows into the positive electrode liquid outlet channel 231, and is discharged from the positive electrode electrolyte outlet 23 through the positive electrode liquid outlet channel 231, completing the flow process of the electrolyte solution in the battery; unlike the commonly used flow channels, the present application adopts an alternately arranged variable diameter structure 26, which can make the electrolyte solution as evenly distributed as possible during the flow process and forced to penetrate into the electrode to participate in the electrochemical reaction.

[0067] Figures 3 to 10 The cross-sectional views of the variable diameter structure 26 of different shapes are shown respectively, and the maximum width of the narrow flow area 264 and the minimum width of the wide flow area 265 of the variable diameter structure 26 can be the same, and the positive projection figure of the periodically alternating variable diameter structure 26 on the bipolar plate body along the electrolyte flow direction is a symmetrical arc, fan or cone; in this embodiment, the positive projection figure of the narrow flow area 264 of the variable diameter structure 26 on the bipolar plate body is a rectangle, and the positive projection figure of the wide flow area 265 on the bipolar plate body is a figure connected by symmetrical arcs, and the maximum width of the narrow flow area 264 and the minimum width of the wide flow area 265 can be the same. Among them, L3 is the maximum width of the narrow flow area 264 of the variable diameter structure 26, L1 is the inflow width of the wide flow area 265 of the variable diameter structure 26, L2 is the maximum width of the wide flow area 265 of the variable diameter structure 26, and L is the horizontal length of the narrow flow area 264 and the wide flow area 265. In a specific implementation, the periodically alternating variable diameter structures 26 all adopt the same structural dimensions, and the maximum width L3 of the narrow flow area 264, the minimum width L1 of the wide flow area 265, and the maximum width L2 of the wide flow area 265 can be reasonably adjusted according to actual conditions, such as L3 = L1 = 2 mm, L2 = 6 mm or L3 = L1 = 3 mm, L2 = 8 mm. Figure 4 The locally enlarged structural diagram of the narrow flow area 264 and the wide flow area 265 of the variable diameter structure 26 is shown, in which the maximum width L3 of the narrow flow area 264 is set to 3mm, the minimum width L1 of the wide flow area 265 is set to 3mm, and the horizontal length L of the narrow flow area and the wide flow area is 5mm; the porous electrode adopts carbon felt with a thickness of 2mm.

[0068] In this embodiment, the branch channels 25 are all connected in a serpentine shape, which can increase the length of the electrolyte solution flow path, so that the electrolyte has enough reaction time in the flow channel, and also promote the electrolyte solution to be fully mixed by turning the flow in different directions of the serpentine flow channel. It should be noted that the flow channel structure provided in this embodiment can be set for the flow channel of the bipolar plate. Specifically, the flow channel is improved on the bipolar plate body. Through the combination of the narrow flow area and the wide flow area of ​​the variable diameter structure 26, when the electrolyte solution flows through the variable diameter structure 26, due to the different shapes, a certain degree of reflux will occur when the electrolyte solution flows, so that the electrolyte is mixed more evenly, and the contact area between the electrolyte solution and the electrode is increased; the positive electrode inlet channel 221, the positive electrode serpentine flow channel and the positive electrode outlet channel 231 are connected by a serpentine shape, which increases the length of the flow path of the electrolyte solution in the flow channel, and the electrolyte solution is mixed evenly through multiple turns of the positive electrode serpentine flow channel.

[0069] In a preferred embodiment of the present invention, Fig.12 As shown, it is a schematic diagram of the main structure of the iron-chromium redox flow battery of an embodiment of the present invention. The main structure of the iron-chromium redox flow battery includes a first end plate 1, a first bipolar plate 2, a positive electrode frame 3, a positive terminal 4 located inside the main structure, a proton membrane 5, a negative terminal 6 located inside the main structure, a negative electrode frame 7, a second bipolar plate 8 and a second end plate 9, and the structures are arranged in sequence. The first bipolar plate and the second bipolar plate in the main structure have the same structure. The present invention application takes the positive electrode side as an example. The iron-chromium redox flow battery bipolar plate includes: a bipolar plate body, an electrolyte inlet 22 on the positive electrode side, a distribution channel 29 on the liquid inlet side, a plurality of branch channels 25 on the liquid inlet side, a plurality of branch channels 25 on the liquid outlet side, a liquid outlet distribution channel 29, an electrolyte outlet 23 on the positive electrode side, and a central active area 28 on the positive electrode side. The liquid inlet channel 221 is a part of the distribution channel 29 on the liquid inlet side, and the liquid outlet channel 231 is a part of the liquid outlet distribution channel 29, which will not be described in detail here.

[0070] Among them, the forked-finger flow channel is in a centrally symmetrical form, the electrolyte inlet 22 on the positive electrode side is connected to the distribution flow channel 29 on the liquid inlet side, and the distribution flow channel 29 on the liquid inlet side is connected to a number of branch channels 25 on the liquid inlet side; the electrolyte outlet 23 on the positive electrode side is connected to the liquid outlet distribution flow channel 29, and the liquid outlet distribution flow channel 29 is connected to a number of branch channels 25 on the liquid outlet side.

[0071] Each branch channel 25 on the liquid inlet side is perpendicular to the distribution channel 29 on the liquid inlet side, and each branch channel 25 on the liquid outlet side is perpendicular to the liquid outlet distribution channel 29. In the vertical direction, each branch channel 25 on the liquid inlet side and each branch channel 25 on the liquid outlet side are parallel to each other, and both the branch channel 25 on the liquid inlet side and the branch channel 25 on the liquid outlet side are located in the middle active area 28 on the positive electrode side.

[0072] The electrolyte enters the distribution channel 29 on the positive electrode inlet side from the positive electrode inlet port, then flows into the electrode through the branch channel 25 on the positive electrode inlet side, completes the corresponding electrochemical reaction, and then convects to the adjacent branch channel 25 on the positive electrode outlet side. Each branch channel 25 on the positive electrode outlet side respectively collects the electrolyte into the positive electrode outlet distribution channel 29, collects the electrolyte through the positive electrode outlet distribution channel 29, and discharges it from the positive electrode outlet port, completing the flow process of the electrolyte.

[0073] The distribution channels 29 on the liquid inlet side, the branch channels 25 on the liquid inlet side, the liquid outlet distribution channels 29 and the branch channels 25 on the liquid outlet side are all of the same structure. In practical applications, the sizes of the liquid inlet and outlet distribution channels 29 and the branch channels 25 on the liquid inlet and outlet sides can be adjusted according to the area of ​​the active area to obtain the best liquid inlet and outlet channel size.

[0074] The interdigitated flow channels in the embodiment of the present invention are distributed symmetrically with respect to the center. The electrolyte inlet 22 on the positive electrode side is connected to the distribution flow channel 29 on the liquid inlet side, and the distribution flow channel 29 on the liquid inlet side is connected to a plurality of branch channels 25 on the liquid inlet side; the positive electrode electrolyte outlet 23 is connected to the liquid outlet distribution flow channel 29, and the liquid outlet distribution flow channel 29 is connected to a plurality of branch channels 25 on the liquid outlet side.

[0075] Among them, a plurality of diameter-changing structures 26 are arranged on the branch channel 25 on the liquid inlet side, each branch channel 25 on the liquid inlet side is perpendicular to the distribution channel 29 on the liquid inlet side, and each branch channel 25 on the liquid outlet side is perpendicular to the liquid outlet distribution channel 29 .

[0076] In this embodiment, each branch channel 25 on the liquid inlet side and each branch channel 25 on the liquid outlet side are parallel to each other in the vertical direction, the minimum spacing between adjacent branch channels 25 on the liquid inlet side and branch channels 25 on the liquid outlet side is 30 mm, and the maximum spacing is 50 mm, and the branch channels 25 on the liquid inlet side and the branch channels 25 on the liquid outlet side are both located in the middle active area 28 on the positive electrode side.

[0077] In this embodiment, the channel width of the main inlet and outlet liquid channel is 8 mm, the channel depth of the main inlet and outlet liquid channel is 4 mm, the channel width of the branch channel 25 on the inlet and outlet liquid side is 3 mm, and the total channel length of the branch channel 25 on the inlet and outlet liquid side is 120 mm; wherein, the length of the branch channel 25 is 15 mm, and the cross-sectional area of ​​the branch channel 25 is 24 mm2; wherein, the maximum cross-sectional area of ​​the branch channel 25 in the second direction is 48 mm2.

[0078] In this embodiment, the bipolar plate body 21 is a non-porous graphite plate, the proton membrane is a speek ion conductive membrane, and the non-porous graphite plate has a thickness of 6 mm and an area size of 2.1 cm×2.1 cm.

[0079] The flow process of electrolyte in the bipolar plate is as follows:

[0080] It should be noted that the variable diameter structure 26 is arranged parallel to the membrane plane and is seamlessly fitted with the electrode. The electrolyte is pumped into the positive electrode inlet, and enters the distribution channel 29 on the positive electrode inlet side from the positive electrode inlet. The electrolyte is distributed to the branch channels 25 on each inlet side through the distribution channel 29 on the positive electrode inlet side. The electrolyte flows into the electrode through the branch channel 25 on the positive electrode inlet side, completes the corresponding electrochemical reaction, and then convects to the branch channel 25 on the adjacent positive electrode outlet side. Then, it flows to the positive electrode outlet distribution channel 29 through the branch channel 25 on the positive electrode outlet side, collects the electrolyte, and is discharged from the electrolyte outlet 23 on the positive electrode side, thereby completing the flow process of the electrolyte in the battery.

[0081] The electrolyte enters the positive electrode inlet and outlet distribution channel 29, first through the branch channel 25, and then through the variable diameter structure 26. Since the width L1 of the branch channel 25 is the same as the maximum width of the narrow flow area of ​​the variable diameter structure 26, the electrolyte can flow completely into the variable diameter structure 26 from the straight flow channel.

[0082] In this embodiment, the bipolar plate flow channel is designed as a forked-finger flow channel, and the contact area between the electrolyte and the electrode can be increased through the variable diameter structure 26, so that the electrolyte is mixed more evenly and the concentration polarization is reduced. At the same time, the design of this structure can promote the flow of the electrolyte and is not easy to block the flow channel.

[0083] The present invention adopts a variable diameter structure 26, and the flow channel used no longer uses a single flow channel design. A combination of multiple flow channels is adopted, and the advantages of different flow channel structures are reasonably used, so that the bipolar plate flow channel has more obvious advantages, effectively increases the contact area between the electrolyte solution and the electrode, makes the electrolyte solution mixed more evenly, has a simple structure, reduces manufacturing costs, and provides convenient conditions for improving the overall performance of the battery.

[0084] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0085] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0086] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) or a processor (processor) to perform all or part of the steps of each implementation method of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program code.

[0087] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above 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.

Claims

1. An iron-chromium redox flow battery bipolar plate, characterized in that: It includes: A bipolar plate body, wherein the bipolar plate body is provided with an electrolyte inlet for the electrolyte of the liquid flow battery to enter and an electrolyte outlet for the electrolyte of the liquid flow battery to flow out, a flow channel is provided between the electrolyte inlet and the electrolyte outlet, and the flow channel includes a plurality of branch channels; A plurality of diameter-changing structures are arranged at intervals on the tube wall of the branch channel; The variable diameter structure is beaded, and the orthographic projection of the variable diameter structure on the bipolar plate body is a symmetrical figure along the first direction and the second direction; the first direction is the flow direction of the electrolyte in the branch channel; the second direction is the direction perpendicular to the flow direction of the electrolyte in the branch channel; The diameter-changing structures are arranged in an array along the flow direction of the electrolyte in the branch channel, and the spacing between adjacent diameter-changing structures is equal or unequal; The variable diameter structure includes two or more single bead structures arranged in sequence along the flow direction of the electrolyte in the branch channel, and the orthographic projection pattern of the single bead structure on the bipolar plate body is mirror-symmetrical in the second direction; The orthographic projection shape of the single bead structure on the bipolar plate body is two mirror-symmetrical arcs, a fan, a cone, or a polygon.

2. The iron-chromium redox flow battery bipolar plate according to claim 1, characterized in that: The diameter-changing structure has a virtual center line perpendicular to the flow direction of the electrolyte in the branch channel along the flow direction of the electrolyte in the branch channel, and the diameter-changing structure is mirror-symmetrical on both sides of the virtual center line.

3. The iron-chromium redox flow battery bipolar plate according to claim 1, characterized in that: The variable diameter structure includes a first single bead structure and a second single bead structure, the first single bead structure and the second single bead structure are sequentially connected in series along the flow direction of the electrolyte in the branch channel; there is a first distance between the first single bead structure and the second single bead structure; There is a second spacing between adjacent diameter-changing structures; the first spacing is smaller than the second spacing; or the first spacing is zero.

4. The iron-chromium redox flow battery bipolar plate according to claim 3, characterized in that: The first single-bead structure and the second single-bead structure are symmetrically arranged along the flow direction of the electrolyte in the branch channel; and a third single-bead structure is arranged between the first single-bead structure and the second single-bead structure.

5. The iron-chromium redox flow battery bipolar plate according to claim 4, characterized in that: The third single-bead structure, the first single-bead structure and the second single-bead structure have the same shape, and the orthographic projection patterns of the single-bead structures on the bipolar plate body are symmetrical along the first direction and the second direction.

6. The iron-chromium redox flow battery bipolar plate according to claim 4, characterized in that: The single bead structure forms a virtual circle or hexagon in the orthographic projection of the bipolar plate body.

7. The iron-chromium redox flow battery bipolar plate according to claim 4, characterized in that: The orthographic projection pattern of the first single-bead structure on the bipolar plate body and the orthographic projection pattern of the second single-bead structure on the bipolar plate body are mirror-symmetric in the first direction, and the orthographic projection pattern of the third single-bead structure on the bipolar plate body is different from the orthographic projection pattern of the second single-bead structure on the bipolar plate body.

8. The iron-chromium redox flow battery bipolar plate according to claim 1, characterized in that: The flow channel includes a liquid inlet channel, a liquid outlet channel and a serpentine flow channel arranged between the liquid inlet channel and the liquid outlet channel. The serpentine flow channel includes an elbow portion and a branch channel. The branch channel is arranged between two adjacent elbow portions or between the elbow portion and the liquid inlet channel, or between the elbow portion and the liquid outlet channel.

9. The iron-chromium redox flow battery bipolar plate according to claim 1, characterized in that: The flow channel comprises a liquid inlet channel, a liquid outlet channel and an interdigitated flow channel arranged between the liquid inlet channel and the liquid outlet channel; the interdigitated flow channel comprises a distribution flow channel and a branch channel connected to the distribution flow channel.

10. An iron-chromium redox flow battery, characterized in that: The iron-chromium redox flow battery comprises the iron-chromium redox flow battery bipolar plate according to any one of claims 1 to 9.

Images