In-situ observation apparatus and method for flow battery

Abstract

The application discloses an in-situ observation device and method of a flow battery, and the in-situ observation device comprises a visual battery and a fastening assembly; the visual battery comprises a positive half-cell, a negative half-cell and an ion exchange membrane, the positive half-cell and the negative half-cell are arranged adjacently, and the ion exchange membrane is clamped between the positive half-cell and the negative half-cell; the positive half-cell and the negative half-cell each comprise a transparent observation plate, a sealing piece and a flow channel plate, and the transparent observation plate, the sealing piece and the flow channel plate are arranged in a laminated mode; a fluid channel and an electrode groove are formed in the flow channel plate, a porous electrode is arranged in the electrode groove, the fluid channel is communicated with the electrode groove, and the electrolyte is guided to flow through the porous electrode; a current collecting and conducting piece is attached in the electrode groove, the current collecting and conducting piece extends to the outside of the flow channel plate to form an electric leading end; and the fastening assembly is used for tightly fixing the visual battery. The application aims to realize in-situ, high-fidelity and whole-process observation on the evolution behavior of metal deposition / dissolution in the battery.

Description

Technical Field

[0001] This application relates to the field of flow battery energy storage technology, specifically to an in-situ observation device and method for flow batteries. Background Technology

[0002] As the global energy structure transitions towards a low-carbon model, large-scale energy storage technology has become crucial for supporting the efficient utilization of renewable energy. Flow batteries, with their advantages of high safety, flexible system design, and environmental friendliness, hold immense promise for large-scale electrochemical energy storage. Among them, deposition-type flow batteries using metal as the negative electrode active material have become a significant direction in current energy storage technology research and commercial application due to the low cost of active materials and high energy density. However, the actual cycle life of such flow batteries is limited by the uneven behavior of metal deposition on the negative electrode side.

[0003] In the existing technology, the in-situ observation device for flow batteries is designed to deviate from the actual working conditions (such as lack of circulating flow field, no membrane separation, simplified electrode shape, etc.), which makes it impossible to conduct in-situ, high-fidelity full-process observation of the metal deposition / dissolution evolution behavior inside the battery, and it is difficult to establish a real-time correlation between battery performance and internal evolution behavior.

[0004] Therefore, how to provide an in-situ observation device and method for flow batteries to achieve in-situ, intuitive, and high-fidelity full-process observation of the metal deposition / dissolution evolution behavior inside flow batteries has become a technical problem that urgently needs to be solved in the field of flow battery energy storage technology. Summary of the Invention

[0005] This application provides an in-situ observation device and method for flow batteries, aiming to solve the technical problem in the prior art that the structural design of the observation device is out of touch with the actual working conditions of the flow battery, resulting in the inability to conduct in-situ, high-fidelity, full-process observation of the metal deposition / dissolution evolution behavior inside the battery.

[0006] On one hand, embodiments of this application provide an in-situ observation device for a flow battery, comprising: a visualized battery and a fastening assembly; wherein, the visualized battery includes a positive electrode half-cell, a negative electrode half-cell, and an ion exchange membrane, the positive electrode half-cell and the negative electrode half-cell being arranged adjacent to each other along a first direction, and the ion exchange membrane being sandwiched between the positive electrode half-cell and the negative electrode half-cell; both the positive electrode half-cell and the negative electrode half-cell include a transparent observation plate, a sealing element, and a flow channel plate, the transparent observation plate, the sealing element, and the flow channel plate being stacked along a second direction, the sealing element being used to prevent electrolyte from seeping out from between the transparent observation plate and the flow channel plate, the first direction being perpendicular to the second direction. The flow channel plate has a fluid channel, and an electrode groove is formed on the side of the flow channel plate facing the ion exchange membrane. A porous electrode is placed in the electrode groove, and the fluid channel is connected to the electrode groove to guide the electrolyte to flow through the porous electrode. A current collector is attached to the electrode groove, and the current collector extends to the outside of the flow channel plate to form a current-leading end. The fastening assembly includes a first fastener and a second fastener. The first fastener is used to press and fix the positive half-cell, the ion exchange membrane and the negative half-cell along the first direction, and the second fastener is used to press and fix the transparent observation plate, the sealing element and the flow channel plate along the second direction.

[0007] Optionally, in some embodiments of this application, the transparent observation plate is made of acrylic material with high light transmittance, and the external dimensions of the transparent observation plate are the same as those of the flow channel plate.

[0008] Optionally, in some embodiments of this application, the ratio of the length of the flow channel plate to the length of the electrode groove is 3:1, the ratio of the width of the flow channel plate to the width of the electrode groove is 3:1, the ratio of the thickness of the flow channel plate to the thickness of the electrode groove is 5:1, and the ratio of the length of the flow channel plate to the width of the flow channel plate is 2:1.

[0009] Optionally, in some embodiments of this application, the current collector is a conductive tape, which is attached to the bottom surface of the electrode groove, and one end of the conductive tape extends to the outside of the flow channel plate to form the current-leading end.

[0010] Optionally, in some embodiments of this application, the seal is a fluororubber gasket, the size of which is configured to cover and shield the electrode groove area.

[0011] Optionally, in some embodiments of this application, the thickness of the conductive tape ranges from 0.055 mm to 0.077 mm, and the thickness of the sealant ranges from 0.4 mm to 0.6 mm.

[0012] Optionally, in some embodiments of this application, the first fastener includes a bolt, a nut, and a fastening clamp. The fastening clamp is disposed on the outermost side of the positive half-cell and the negative half-cell, and the bolt passes through the fastening clamp and is locked by tightening the nut.

[0013] Optionally, in some embodiments of this application, the in-situ observation device further includes: a charge-discharge tester, electrically connected to the current collector via the lead-in terminal, for controlling and monitoring the charge-discharge process of the visualized battery; an optical microscope, disposed on the outside of the transparent observation plate, for observing the dynamic evolution behavior of zinc inside and at the interface of the porous electrode in real time through the transparent observation plate; and a host computer control system, electrically connected to the charge-discharge tester and the optical microscope respectively, for synchronously acquiring and recording the electrochemical performance data output by the charge-discharge tester and the microscopic image data output by the optical microscope.

[0014] Optionally, in some embodiments of this application, the in-situ observation device further includes: a positive electrolyte storage tank and a negative electrolyte storage tank, wherein the positive electrolyte storage tank is used to store positive electrolyte and the negative electrolyte storage tank is used to store negative electrolyte; a positive peristaltic pump and a negative peristaltic pump, wherein the positive peristaltic pump is disposed on the positive electrolyte pipeline and the negative peristaltic pump is disposed on the negative electrolyte pipeline, and both the positive and negative peristaltic pumps are used to drive the electrolyte to circulate; the positive electrolyte pipeline and the negative electrolyte pipeline are respectively connected to the fluid channels of the positive half-cell and the negative half-cell to form a closed-loop circulation circuit.

[0015] On the other hand, this application provides an in-situ observation method for flow batteries, employing the in-situ observation device for flow batteries as described above. The in-situ observation method includes the following steps: introducing fluid into the interior of the visualized battery and checking the sealing between the transparent observation plate and the flow channel plate, and between the positive electrode half-cell and the negative electrode half-cell; placing the visualized battery within the observation field of view to acquire images of the electrode groove; applying a charge / discharge current to the visualized battery and acquiring real-time images of the metal deposition or dissolution evolution behavior within the electrode groove; correlating and comparing the electrochemical data from the charge / discharge test with the dynamic image data to establish a correspondence between the dynamic evolution behavior of the metal and the performance of the visualized battery.

[0016] The in-situ observation device and method for flow batteries provided in this application have the following advantages compared with the prior art: (1) The structure is realistic and the observation fidelity is high. This application constructs an internal structure that is highly consistent with the real flow battery system by setting up positive / negative half-cells, ion exchange membranes sandwiched between the two, and electrode grooves and fluid channels opened in the flow channel plate in each half-cell. The transparent observation plate provides an optical path directly as an outer window without the need to introduce additional sensors or other invasive components. Without changing the original internal structure and reaction environment of the battery, in-situ observation of the metal deposition / dissolution behavior in the porous electrodes in the electrode groove is realized, ensuring that the observation results can truly reflect the dynamic evolution law under actual working conditions.

[0017] (2) It has reliable sealing and ensures long-term stable operation. This application has a sealing element between the transparent observation plate and the flow channel plate of each half cell, and a fastening assembly is used to press and fix the positive electrode half cell, ion exchange membrane and negative electrode half cell as a whole. This sealing and fastening synergistic structure effectively prevents electrolyte from seeping out from the interlayer interface and cross-contamination between the positive and negative electrode electrolytes, ensuring the long-term sealing reliability of the device under actual operating pressure, and providing engineering feasibility for continuous observation during continuous charge and discharge cycles.

[0018] (3) It is highly versatile and applicable to the evaluation of various flow battery systems. The device structure of this application does not depend on specific electrolyte components and can be used in various deposition-type flow battery systems with metal as the negative electrode active material. It can also be used to compare and evaluate the effects of different electrode materials, different types of separators and their combinations on suppressing metal dendrite growth, providing an efficient experimental platform for the optimization and screening of flow battery system components. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the in-situ observation device for flow batteries provided in the embodiments of this application; Figure 2 This is a schematic diagram of the overall assembly structure of a visualized battery provided in an embodiment of this application; Figure 3 for Figure 2 The image shows a top view of the visualized battery. Figure 4 for Figure 2 The image shows a side view of the visualized battery. Figure 5 for Figure 2 The diagram shows the exploded structure of the battery. Figure 6 This is a schematic diagram of the structure of an in-situ observation device for a flow battery provided in another embodiment of this application; Figure 7 A flowchart illustrating the in-situ observation method for flow batteries provided in this application embodiment; Figure 8This is a time-series image of zinc evolution in a fully charged-discharge cycle of a battery, as shown in Embodiment 1 of this application, along with its corresponding voltage-time curve. Figure 9 This is a time-series image of the morphological evolution of zinc deposits penetrating the ion exchange membrane in Example 2 of this application, along with its corresponding voltage-time curve. Figure 10 These are comparative images of the dynamic evolution morphology of zinc under different electrolyte systems in Example 3 of this application; Figure 11 for Figure 10 The diagram shows a comparison of the battery voltage-time curves for each electrolyte system. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings. The described technical solutions are for illustrative purposes only and should not be construed as limiting the scope of protection of this application.

[0021] like Figure 1 As shown, an embodiment of this application provides an in-situ observation device 100 for a flow battery, which includes at least: a visualization battery 1 and a fastening assembly 2.

[0022] like Figures 2 to 5 As shown, the in-situ visualized battery 1 has a symmetrical structure, including a positive electrode half-cell, a negative electrode half-cell, and an ion exchange membrane 23 sandwiched between them. The positive electrode half-cell and the negative electrode half-cell are aligned along a first direction (i.e., the horizontal left-right direction, as shown in the image). Figure 2 (As shown by the middle arrow X) Adjacent to each other, the ion exchange membrane 23 is sandwiched between the positive and negative half-cells. Preferably, the in-situ visualized battery 1 is a zinc-based flow battery.

[0023] In the embodiments of this application, the positive half-cell and the negative half-cell have a completely symmetrical structure. Taking one half-cell as an example, each half-cell includes a transparent observation plate 18, a sealing member 19, and a flow channel plate 22. The transparent observation plate 18, the sealing member 19, and the flow channel plate 22 are along the second direction (i.e., the vertical up-down direction, such as...). Figure 2 As indicated by the middle arrow Y, the layers are stacked, with the transparent observation plate 18 located on the top layer (outer side), the sealant 19 located in the middle layer, and the sealant 19 used to prevent electrolyte from seeping out between the transparent observation plate 18 and the flow channel plate 22. The flow channel plate 22 is located on the bottom layer (inner side, i.e., the side facing the ion exchange membrane 23). The first direction (the direction opposite to the positive and negative electrodes) is perpendicular to the second direction (the stacking direction of the observation plate and the flow channel plate).

[0024] In the embodiments of this application, the transparent observation plate 18 is made of a transparent material with high light transmittance, preferably a highly transparent acrylic material, to ensure optical transmittance and facilitate machining.

[0025] The overall dimensions of the flow channel plate 22 are 60mm (length) × 30mm (width) × 10mm (thickness). Fluid channels are formed on the flow channel plate 22 (the flow path is not specifically shown in the figure), and electrode grooves defining an electrode region are formed on the side facing the ion exchange membrane 23 (i.e., the lower surface or inner surface of the flow channel plate 22). The electrode groove region has dimensions of 20mm (length) × 10mm (width) × 2mm (depth) and is used to accommodate the porous electrode 20.

[0026] In the embodiments of this application, the external dimensions of the transparent observation plate 18 are the same as those of the flow channel plate 22.

[0027] In the embodiments of this application, the fluid channel on the flow channel plate 22 is connected to the electrode groove, and the two ends of the fluid channel are respectively connected to the electrolyte inlet and the electrolyte outlet, which are used to guide the electrolyte into the electrode groove, flow through the porous electrode 20 and then out, forming a forced convection circulation through the interior of the porous electrode 20. The flow channel plate 22 is also provided with a through hole for fixing, which extends along the thickness direction of the flow channel plate 22, for the second fastener 2B and the first fastener 2A to pass through.

[0028] Preferably, the length ratio of the flow channel plate 22 to the length of the electrode groove is approximately 3:1 (60mm:20mm), the width ratio of the flow channel plate 22 to the width of the electrode groove is approximately 3:1 (30mm:10mm), the thickness ratio of the flow channel plate 22 to the thickness of the electrode groove is approximately 5:1 (10mm:2mm), and the length ratio of the flow channel plate 22 to its width is approximately 2:1 (60mm:30mm). These dimensional ratios ensure that the flow channel plate 22 has sufficient structural strength to withstand fastening pressure and internal fluid pressure, while providing ample peripheral area for arranging fluid channels and seals 19 in the electrode groove, ensuring uniform fluid distribution and reliable sealing.

[0029] In the embodiments of this application, the flow channel plate 22 is integrally formed by CNC machining or laser engraving of high transparency acrylic material to ensure the dimensional accuracy and surface smoothness of the flow channel.

[0030] In the embodiments of this application, the porous electrode 20 is placed in the electrode groove of the flow channel plate 22. The size of the porous electrode 20 is adapted to the size of the electrode groove, that is, the size of the porous electrode 20 is 20mm (length) × 10mm (width) × 2mm (thickness), and the porous electrode 20 fills the electrode groove. The porous electrode 20 adopts the three-dimensional porous conductive material actually used in flow batteries, preferably graphite felt or carbon felt. Graphite felt has a three-dimensional network fiber structure, which can provide a substrate with a high specific surface area for metal deposition, while allowing the electrolyte to flow freely, truly replicating the electrode environment under actual operating conditions of flow batteries.

[0031] In the embodiments of this application, the porous electrode 20 is in electrical contact with the current-collecting conductive tape 21 to collect the current generated by the electrode reaction or to apply external current to the electrode.

[0032] In the embodiments of this application, the current collector is attached to the inner wall of the electrode groove, preferably to the lower bottom surface of the electrode groove (i.e., the inner bottom surface of the flow channel plate 22). One end of the current collector extends to the outside of the flow channel plate 22 to form a current-leading end, which facilitates connection with the positive terminal connection wire 5 or the negative terminal connection wire 6 of the charge-discharge tester 8.

[0033] In the embodiments of this application, the current collector is preferably made of conductive tape 21, more preferably of copper conductive tape (i.e., conductive copper tape). The thickness of the conductive tape 21 is approximately 0.066 mm, and can range from 0.055 mm to 0.077 mm. Within this thickness range, the conductive tape 21 has sufficient conductive cross-sectional area to carry the charging and discharging current, without raising the position of the porous electrode 20 or affecting the depth accuracy of the electrode groove due to excessive thickness. The conductive tape 21 has good flexibility and adhesion, and can be tightly attached to the bottom surface of the electrode groove, with one end extending to the outside of the flow channel plate 22 to form a current-leading end.

[0034] In the embodiments of this application, using conductive tape 21 as the current collector has the following significant advantages: First, the conductive tape 21 is extremely thin (approximately 0.066 mm), hardly changing the effective depth of the electrode groove, and does not affect the installation of the porous electrode 20 or the flow distribution of the electrolyte. Second, the adhesive layer of the conductive tape 21 can form a tight fit with the bottom surface of the flow channel plate 22, making it less prone to falling off or shifting during use, thus ensuring the stability of the current collection. Third, the external lead-in end of the conductive tape 21 has good flexibility, facilitating connection with external wires without occupying additional observation space. Finally, the conductive tape 21 is inexpensive and easy to replace, reducing the maintenance cost of the experimental setup.

[0035] In the embodiments of this application, a sealing member 19 is disposed between the transparent observation plate 18 and the flow channel plate 22, and arranged along the periphery of the electrode groove, for sealing the gap between the transparent observation plate 18 and the flow channel plate 22 to prevent electrolyte from seeping out from between the transparent observation plate 18 and the flow channel plate 22. The dimensions of the sealing member 19 are configured to cover and shield the electrode groove area, and its inner edge contour is consistent with the outer edge contour of the electrode groove. In this embodiment, the overall dimensions of the sealing member 19 are 20mm (length) × 10mm (width) × 0.5mm (thickness), which is the same as the opening size of the electrode groove (20mm × 10mm). The sealing member 19 is cut along the outer periphery of the electrode groove area to form a frame-shaped or gasket-shaped structure consistent with the opening contour of the electrode groove, and is arranged around the periphery of the electrode groove in a manner that shields the electrode groove area.

[0036] In the embodiments of this application, the sealing element 19 is preferably a fluororubber gasket. Fluororubber has excellent chemical corrosion resistance, high temperature resistance, and good elastic deformation ability, and can withstand the chemical erosion of the strong acid or strong alkaline electrolyte of the flow battery for a long time without swelling or aging, ensuring the long-term reliability of the seal. The thickness of the sealing element 19 is approximately 0.5 mm, and the value can be between 0.4 mm and 0.6 mm. Within this thickness range, the sealing element 19 can generate sufficient compressive deformation under tightening pressure to fill the micro-uneven gap between the transparent observation plate 18 and the flow channel plate 22, while avoiding excessive compression that could cause the sealing element 19 to be squeezed out or deformed or obstruct the effective observation area of ​​the electrode groove.

[0037] In the embodiments of this application, the sealing element 19 is arranged on the periphery of the electrode groove rather than inside the electrode groove, ensuring that the sealing element 19 will not block the optical observation path of the transparent observation plate 18 to the porous electrode 20 inside the electrode groove, thus achieving compatibility between the sealing function and the observation function.

[0038] In the embodiments of this application, the ion exchange membrane 23 is sandwiched between the flow channel plate 22 of the positive electrode half-cell and the flow channel plate 22 of the negative electrode half-cell. The ion exchange membrane 23 is used to separate the positive electrode electrolyte and the negative electrode electrolyte, preventing them from directly mixing and causing cross-contamination, while allowing charge balance ions (such as H+) to pass through. + OH - (Or other supporting electrolyte ions) migrate between the positive and negative electrodes to form a complete conductive circuit. The ion exchange membrane 23 can be a cation exchange membrane, an anion exchange membrane, or a porous membrane, and the specific type is selected according to the actual needs of the flow battery system under study (such as zinc-based flow batteries, iron-chromium flow batteries, vanadium redox flow batteries, etc.). The external dimensions of the ion exchange membrane 23 are the same as or slightly larger than the external dimensions of the flow channel plate 22 to ensure complete coverage of the electrode groove area and prevent cross-contamination of the positive and negative electrode electrolytes.

[0039] In embodiments of this application, the in-situ observation device for the flow battery further includes a fastening assembly 2, which is used to press and fix the visualization battery 1. Specifically, the fastening assembly 2 includes a first fastener 2A and a second fastener 2B.

[0040] In the embodiments of this application, the first fastener 2A is used to press and fix the positive electrode half-cell, ion exchange membrane 23 and negative electrode half-cell along the first direction X (the direction between the positive and negative electrodes, i.e., the horizontal left-right direction). In this embodiment, the first fastener 2A is an integral fastener, specifically an M8 bolt 15 and an M8 nut 24.

[0041] Furthermore, the first fastener 2A also includes a fastening clamp 16, which is located on the outermost side of the positive half-cell and the negative half-cell (i.e., the outer side of the transparent observation plate 18). After the M8 bolt 15 passes through the fastening clamp 16, it is locked by tightening the M5 nut 24 to distribute the clamping force more evenly on the entire surface of the transparent observation plate 18.

[0042] In the embodiments of this application, the second fastener 2B is used to press and fix the transparent observation plate 18, the seal 19, and the flow channel plate 22 along the second direction Y (the stacking direction of the observation plate and the flow channel plate, i.e., the vertical up-down direction). In this embodiment, the second fastener 2B is specifically an M5 bolt 17 and an M5 nut 25.

[0043] like Figures 1 to 5 As shown, the second fastener 2B passes through the corresponding through holes on the transparent observation plate 18, the seal 19, and the flow channel plate 22. Tightening the M5 nut 25 secures the three components together, forming a single half-cell assembly. This clamping force causes the seal 19 to compress and deform, filling the microscopic gap between the transparent observation plate 18 and the flow channel plate 22, achieving effective sealing inside the half-cell and preventing electrolyte from seeping out (i.e., leaking outwards) from between the transparent observation plate 18 and the flow channel plate 22.

[0044] In the embodiments of this application, the second fastener 2B first pre-assembles the transparent observation plate 18, the seal 19 and the flow channel plate 22 into an integral half-cell unit, and then the first fastener 2A presses the two half-cells and the ion exchange membrane 23 together.

[0045] This double-layer fastening structure design of "partial pre-tightening followed by overall fastening" has the following advantages: on the one hand, it ensures a reliable seal between the transparent observation plate 18 and the flow channel plate 22 inside each half-cell; on the other hand, it ensures an overall seal between the positive and negative electrode half-cells and the ion exchange membrane 23; at the same time, the partially pre-tightened half-cell units facilitate the disassembly, cleaning, and replacement of vulnerable parts such as the porous electrode 20 and the sealing element 19, thereby improving the ease of maintenance of the device.

[0046] like Figure 6As shown, the in-situ observation device 100 for a flow battery according to this application embodiment, based on the visualized battery 1, also includes the following system-level components to form a complete in-situ observation system for a flow battery.

[0047] The charge / discharge tester 8 is electrically connected to the leads of the current collector (conductive tape 21) of the positive half-cell and the negative half-cell via the positive electrode connecting wire 5 and the negative electrode connecting wire 6, respectively. The charge / discharge tester 8 is used to apply charge / discharge current to the visualized battery according to a preset charge / discharge strategy (such as constant current charge / discharge, constant voltage charge, constant current / constant voltage combined charge / discharge, or simulated dynamic charge / discharge under simulated operating conditions, etc.), and to monitor the battery's electrochemical performance parameters such as voltage, current, capacity, coulombic efficiency, and energy efficiency in real time.

[0048] An optical microscope 7 is positioned outside (above) the transparent observation plate 18, with its objective lens facing the transparent observation plate 18. The optical microscope 7 is used to observe in real time the dynamic evolution of the metal inside and at the interface of the porous electrode 20, such as zinc deposition or dissolution, through the transparent observation plate 18. The optical microscope 7 can be a stereomicroscope (for macroscopic observation), a metallurgical microscope, or a confocal microscope (for microscopic observation), and its resolution can be flexibly selected according to research needs. The microscopic image data output by the optical microscope 7 is transmitted to the host computer control system 3 via the image signal transmission line 4.

[0049] The host computer control system 3 is electrically connected to the charge / discharge tester 8 and the optical microscope 7, respectively. Specifically, it is connected to the charge / discharge tester 8 via a data cable and to the optical microscope 7 via an image signal transmission line 4. The host computer control system 3 is used to synchronously acquire and record the electrochemical performance data output by the charge / discharge tester 8 and the microscopic image data output by the optical microscope 7, and to ensure that the time axes of the two are precisely synchronized.

[0050] A positive electrolyte storage tank 11 stores the positive electrolyte, and a negative electrolyte storage tank 14 stores the negative electrolyte. A positive peristaltic pump 10 is installed on the positive electrolyte pipeline 9, and a negative peristaltic pump 13 is installed on the negative electrolyte pipeline 12. Both are used to drive the electrolyte to circulate in a closed-loop circuit. The positive electrolyte pipeline 9 connects the positive electrolyte storage tank 11 to the fluid channel on the flow channel plate 22 of the positive half-cell, and the negative electrolyte pipeline 12 connects the negative electrolyte storage tank 14 to the fluid channel on the flow channel plate 22 of the negative half-cell, forming closed-loop circuits on the positive and negative sides, respectively. Driven by the peristaltic pumps, the electrolyte flows from the storage tank through the pipeline into the fluid channel of the flow channel plate 22, enters the electrode tank, flows through the porous electrode 20, and then returns to the storage tank through the fluid channel outlet and pipeline, forming a continuous circulation flow, thereby simulating the convective mass transfer environment of a real flow battery.

[0051] The in-situ observation device for flow batteries provided in this application has the following advantages compared to the prior art: (1) The structure is realistic and the observation fidelity is high. This application constructs an internal structure that is highly consistent with the real flow battery system by setting up positive / negative half-cells, ion exchange membranes sandwiched between the two, and electrode grooves and fluid channels opened in the flow channel plate in each half-cell. The transparent observation plate provides an optical path directly as an outer window without the need to introduce additional sensors or other invasive components. Without changing the original internal structure and reaction environment of the battery, in-situ observation of the metal deposition or dissolution behavior in the porous electrodes in the electrode groove is realized, ensuring that the observation results can truly reflect the dynamic evolution law under actual working conditions.

[0052] (2) It has reliable sealing and ensures long-term stable operation. This application has a sealing element between the transparent observation plate and the flow channel plate of each half cell, and a fastening assembly is used to press and fix the positive electrode half cell, ion exchange membrane and negative electrode half cell as a whole. This sealing and fastening synergistic structure effectively prevents electrolyte from seeping out from the interlayer interface and cross-contamination between the positive and negative electrode electrolytes, ensuring the long-term sealing reliability of the device under actual operating pressure, and providing engineering feasibility for continuous observation during continuous charge and discharge cycles.

[0053] (3) It is highly versatile and applicable to the evaluation of various flow battery systems. The device structure of this application does not depend on specific electrolyte components and can be used in various deposition-type flow battery systems with metal as the negative electrode active material. It can also be used to compare and evaluate the effects of different electrode materials, different types of separators and their combinations on suppressing metal dendrite growth, providing an efficient experimental platform for the optimization and screening of flow battery system components.

[0054] like Figure 7 As shown, this application also provides an in-situ observation method for flow batteries, which employs the in-situ observation device for flow batteries described above (see [link to relevant documentation]). Figures 1 to 6 The method specifically includes the following steps.

[0055] Step S10: Introduce fluid into the interior of the visualized battery and check the seal between the transparent observation plate and the flow channel plate, as well as between the positive half-cell and the negative half-cell.

[0056] Specifically, the in-situ observation device is assembled according to the pre-set structure.

[0057] First, conductive tape 21 is attached to the bottom surface of the electrode groove of the flow channel plate 22, and one end of conductive tape 21 extends to the outside of the flow channel plate 22 to form a lead-in terminal; porous electrode 20 (graphite felt) is placed in the electrode groove; sealing element 19 (fluororubber gasket) is arranged along the periphery of the electrode groove on the upper surface of the flow channel plate 22; transparent observation plate 18 is placed over sealing element 19, so that the through hole on transparent observation plate 18 is aligned with the through hole on flow channel plate 22; the second fastener (M5 bolt 17 and M5 nut 25, i.e., second fastener 2B) is passed through the through hole and tightened to fasten transparent observation plate 18, sealing element 19 and flow channel plate 22 into one unit to form a single half-cell assembly.

[0058] Similarly, assemble the other half-cell assembly in the same way.

[0059] Then, the ion exchange membrane 23 is clamped between the flow channel plates 22 of the two half-cell components, so that the ion exchange membrane 23 covers the two electrode slot areas. Fastening plates 16 are placed on the outermost sides of the positive half-cell and the negative half-cell, respectively. The first fasteners 2A (M8 bolts 15 and M8 nuts 24) are passed through the through holes of the fastening plates 16 and each layer of components and tightened to press and fix the positive half-cell, ion exchange membrane 23 and negative half-cell along the first direction, thus completing the assembly of the in-situ visualized battery 1.

[0060] Then, connect the positive electrolyte line 9 and the negative electrolyte line 12 to their respective circulation loops (i.e., the fluid channel connecting the positive electrolyte tank 11, the positive peristaltic pump 10, and the positive half-cell, and the fluid channel connecting the negative electrolyte tank 14, the negative peristaltic pump 13, and the negative half-cell). Start the circulation pumps (positive peristaltic pump 10 and negative peristaltic pump 13) to drive the electrolyte to circulate inside the visible battery.

[0061] After introducing the fluid (electrolyte), focus on checking the sealing performance between the transparent observation plate 18 and the flow channel plate 22 (the interface sealed by the seal 19), and between the positive half-cell and the negative half-cell (the interface sealed by the ion exchange membrane 23), to ensure that there is no leakage in the system under actual operating pressure. If leakage is found, the torque of the fasteners needs to be readjusted or the seal needs to be replaced until the seal is satisfactory.

[0062] Step S20: Place the visualization battery within the observation field of view to obtain an image of the electrode slot.

[0063] Specifically, the in-situ visualized battery 1, which has passed the sealing check, is placed within the observation field of the optical microscope 7 (i.e., placed on the stage of the optical microscope 7). The focal length and light source brightness of the optical microscope 7 are adjusted until a clear microscopic image of the porous electrode 20 is obtained in the monitoring screen of the host computer control system 3. This step ensures that the optical path is clear and the imaging quality meets the observation requirements, providing a prerequisite for subsequent real-time image acquisition.

[0064] Simultaneously, the positive electrode connection wire 5 and the negative electrode connection wire 6 of the charge / discharge tester 8 are reliably connected to the leads of the conductive tape 21 of the positive and negative half-cells, respectively. The real-time voltage signal is monitored by the host computer control system 3 to confirm that the circuit loop is unobstructed and that there are no abnormal contact resistances or open circuits. This step ensures the normal operation of the electrochemical testing circuit, providing hardware support for subsequent synchronous data acquisition.

[0065] Step S30: Apply charging and discharging current to the visualized battery and acquire real-time images of the metal deposition or dissolution evolution behavior in the electrode groove.

[0066] Specifically, the charge-discharge electrochemical testing strategy (such as setting parameters like current density, charge-discharge cutoff voltage, and number of cycles) is configured in the host computer control system 3, and the image acquisition module is started simultaneously. At the instant the charge-discharge tester 8 starts its charge-discharge program, the real-time recording function of the optical microscope 7 is activated to ensure that the time axis of the electrochemical signal is completely synchronized with the time axis of the dynamic morphology image.

[0067] During the test (i.e., the entire charge-discharge cycle), the optical microscope 7, through the transparent observation plate 18, captures in real time the dynamic evolution of the metal inside the porous electrode 20 within the electrode slot. This dynamic evolution includes, but is not limited to: the initial formation of metal deposition nuclei, the growth morphology evolution of metal dendrites, the dissolution process of the metal deposition layer, and the possible transmembrane puncture phenomenon of metal dendrites penetrating the ion exchange membrane 23. Simultaneously, the host computer control system 3 records the corresponding voltage-time curves, current-time curves, and capacity and other electrochemical data in real time using the charge-discharge tester 8.

[0068] Step S40: Correlate and compare the electrochemical data from the charge-discharge test with the dynamic image data to establish the correspondence between the dynamic evolution behavior of the metal and the performance of the visualized battery.

[0069] After the test is completed, the raw electrochemical data (including voltage-time curves, etc.) generated by the charge-discharge test are exported from the host computer control system 3, and the stored dynamic evolution video is processed by frame extraction to obtain the microscopic image frames corresponding to each time node.

[0070] Then, characteristic signal points in the electrochemical data (such as characteristic fluctuation points of the voltage curve, voltage drop points, capacity decay inflection points, etc.) are correlated and compared with the corresponding microscopic image frames. Through this spatiotemporal correlation analysis method, a real-time correspondence between the dynamic evolution behavior of metals and battery performance can be established, thereby revealing the dynamic evolution law of metals in the flow battery system.

[0071] Specifically, this method can be used to: intuitively evaluate the actual effects of different electrode materials, different separator types, different electrolyte components, and their combinations on suppressing metal dendrite growth and improving battery cycle stability. By comparing the data correlation analysis results of different experimental groups, the optimal material combinations and operating parameters can be accurately selected, providing direct experimental basis for the performance optimization of flow battery systems.

[0072] Example 1: This embodiment utilizes the in-situ observation device 100 for the aforementioned flow battery to characterize the dynamic evolution behavior of zinc in a zinc-based flow battery under a complete charge-discharge cycle in real time. The experiment used a 1 mol / L zinc chloride (ZnCl2) solution as the electrolyte, a three-dimensional porous electrode made of graphite felt, and a zinc sheet placed below the positive electrode graphite felt as the active material source. The separator was a Nafion 212 ion-exchange membrane. The charge-discharge current density was set to 20 mA / cm², the charging time to 1 hour, and the discharge cutoff voltage to -0.5 V. Figure 8 As shown, in the initial stage of charging, silvery-white metallic zinc begins to precipitate on the surface of the graphite felt fibers near the separator on the negative electrode. As charging continues, the thickness of the precipitated zinc layer gradually increases, and the entire charge-discharge curve remains stable with no significant voltage fluctuations. Upon entering the discharge stage, the zinc deposited on the negative electrode begins to gradually peel off and dissolve, while zinc deposition occurs simultaneously on the positive electrode side. Even after discharge, a small amount of metallic zinc remains on the negative electrode side, clearly visible through a transparent observation plate. Through... Figure 8 Analysis of the charge and discharge data yielded a coulombic efficiency of 92% for the battery. This quantitative calculation result is highly consistent with the physical phenomenon observed in situ that "zinc remains even after discharge."

[0073] Example 2: This embodiment utilizes the in-situ observation device 100 for the aforementioned flow battery to focus on observing the zinc-based flow battery's zinc permeation failure behavior during the later stages of charging and under high zinc areal capacity conditions. For example... Figure 9As shown, in the high areal capacity state during the later stages of charging, although the zinc deposition on the negative electrode is relatively large in the initial stage, it has not yet penetrated the separator, and the charging voltage remains at a high potential. As the charging process continues, the deposited zinc layer grows further in the thickness direction and penetrates the ion exchange membrane. When charging reaches approximately 1000 s, a clear zinc deposition penetration site can be clearly observed on the edge of the positive electrode graphite felt on the right side of the membrane (as shown in the red dashed box). Simultaneously, the charging voltage drops sharply due to an internal local short circuit, achieving a precise correspondence between the failure morphology and abnormal electrical signals. As the charging process progresses further to approximately 1800 s, the zinc deposition penetration area continues to expand. At this point, the rate of decrease in charging voltage slows down and stabilizes, indicating an intensified internal short circuit. This embodiment visually demonstrates the entire evolution process of zinc penetration failure under high areal capacity.

[0074] Example 3: This embodiment utilizes the in-situ observation device 100 for the aforementioned flow battery to compare and analyze the effects of different electrolyte systems (without a supporting electrolyte and with a supporting electrolyte containing 2M KCl) on the dynamic evolution behavior of zinc and battery performance. The experimental current density was set at 40 mA / cm². Figure 10 and Figure 11 As shown, in the system without a supporting electrolyte, the charging voltage is high due to the low electrolyte conductivity, and the in-situ morphology shows ( Figure 10 In sections a1-d1), zinc deposition is highly concentrated in the interface region near the separator. This rapid localized accumulation leads to a sharp drop in the voltage curve at approximately 950 s, indicating that the battery failed due to a short circuit caused by zinc penetration through the separator. After this, the zinc deposition rate slows down significantly. In contrast, adding 2M KCl to support the electrolyte significantly improves the system's conductivity and drastically reduces the charging platform voltage, as demonstrated by the visualization results (…). Figure 10 Figures a2-d2 visually demonstrate that zinc deposition is no longer confined to the membrane surface, but is distributed more deeply and uniformly within the three-dimensional porous electrode (as shown by the red arrow in d2, its deposition depth is significantly greater than that in d1), thereby effectively mitigating the risk of local short circuits at the interface. This embodiment, through the synergistic analysis of morphological evolution and voltage curves, visually confirms the crucial role of the supporting electrolyte in regulating zinc deposition distribution and improving system stability.

[0075] The above provides a detailed description of an in-situ observation device and method for a flow battery as described in the embodiments of this application. The description of the above embodiments is only for the purpose of helping to understand the core ideas of this application, and the above description should not be construed as a limitation on the scope of protection of this application.

Claims

1. An in-situ observation device for a flow battery, characterized in that, include: Visualize the battery and fastening components; The visualized battery includes a positive half-cell, a negative half-cell, and an ion exchange membrane. The positive half-cell and the negative half-cell are arranged adjacent to each other along a first direction, and the ion exchange membrane is sandwiched between the positive half-cell and the negative half-cell. Both the positive electrode half-cell and the negative electrode half-cell include a transparent observation plate, a sealing element, and a flow channel plate. The transparent observation plate, the sealing element, and the flow channel plate are stacked along a second direction. The sealing element is used to prevent electrolyte from seeping out between the transparent observation plate and the flow channel plate. The first direction is perpendicular to the second direction. The flow channel plate has a fluid channel, and the flow channel plate has an electrode groove on the side facing the ion exchange membrane. A porous electrode is placed in the electrode groove, and the fluid channel is connected to the electrode groove to guide the electrolyte to flow through the porous electrode. A current-collecting conductive element is attached to the electrode groove, and the current-collecting conductive element extends to the outside of the flow channel plate to form a current-leading end. The fastening assembly includes a first fastener and a second fastener. The first fastener is used to press and fix the positive half-cell, the ion exchange membrane and the negative half-cell along the first direction. The second fastener is used to press and fix the transparent observation plate, the seal and the flow channel plate along the second direction.

2. The in-situ observation device for a flow battery according to claim 1, characterized in that, The transparent observation plate is made of acrylic material with high light transmittance, and the external dimensions of the transparent observation plate are the same as those of the flow channel plate.

3. The in-situ observation device for a flow battery according to claim 1 or 2, characterized in that, The ratio of the length of the flow channel plate to the length of the electrode groove is 3:1, the ratio of the width of the flow channel plate to the width of the electrode groove is 3:1, the ratio of the thickness of the flow channel plate to the thickness of the electrode groove is 5:1, and the ratio of the length of the flow channel plate to the width of the flow channel plate is 2:

1.

4. The in-situ observation device for a flow battery according to claim 3, characterized in that, The current collector is a conductive tape, which is attached to the bottom surface of the electrode groove, and one end of the conductive tape extends to the outside of the flow channel plate to form the current lead end.

5. The in-situ observation device for a flow battery according to claim 4, characterized in that, The sealing element is a fluororubber gasket, the size of which is configured to cover and shield the electrode groove area.

6. The in-situ observation device for a flow battery according to claim 5, characterized in that, The thickness of the conductive tape ranges from 0.055 mm to 0.077 mm, and the thickness of the seal ranges from 0.4 mm to 0.6 mm.

7. The in-situ observation device for a flow battery according to claim 1, characterized in that, The first fastener includes a bolt, a nut, and a fastening clamp. The fastening clamp is located on the outermost side of the positive half-cell and the negative half-cell. The bolt passes through the fastening clamp and is locked by tightening the nut.

8. The in-situ observation device for a flow battery according to claim 1, characterized in that, The in-situ observation device also includes: A charge-discharge tester is electrically connected to the current collector via the lead-in terminal, and is used to control and monitor the charging and discharging process of the visualized battery. An optical microscope is set on the outside of the transparent observation plate to observe the dynamic evolution of zinc inside and at the interface of the porous electrode in real time through the transparent observation plate. The host computer control system is electrically connected to the charge-discharge tester and the optical microscope, respectively, and is used to synchronously acquire and record the electrochemical performance data output by the charge-discharge tester and the microscopic image data output by the optical microscope.

9. The in-situ observation device for a flow battery according to claim 8, characterized in that, The in-situ observation device also includes: A positive electrode electrolyte storage tank and a negative electrode electrolyte storage tank, wherein the positive electrode electrolyte storage tank is used to store the positive electrode electrolyte and the negative electrode electrolyte storage tank is used to store the negative electrode electrolyte; A positive electrode peristaltic pump and a negative electrode peristaltic pump are provided. The positive electrode peristaltic pump is installed on the positive electrode electrolyte pipeline, and the negative electrode peristaltic pump is installed on the negative electrode electrolyte pipeline. Both the positive electrode peristaltic pump and the negative electrode peristaltic pump are used to drive the electrolyte to circulate. The positive electrolyte pipeline and the negative electrolyte pipeline are respectively connected to the fluid channels of the positive half-cell and the negative half-cell, forming a closed-loop circulation circuit.

10. An in-situ observation method for flow batteries, characterized in that, The in-situ observation device for a flow battery as described in any one of claims 1 to 9, wherein the in-situ observation method comprises the following steps: Fluid is introduced into the interior of the visualized battery, and the sealing between the transparent observation plate and the flow channel plate, as well as between the positive half-cell and the negative half-cell, is checked. The visualized battery is placed within the observation field of view to obtain an image of the electrode slot; A charging and discharging current is applied to the visualized battery, and real-time images are acquired of the metal deposition or dissolution evolution behavior in the electrode groove; By correlating and comparing the electrochemical data from charge-discharge tests with dynamic image data, a correspondence between the dynamic evolution behavior of the metal and the performance of the visualized battery is established.

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