Flow battery test platform

Abstract

The invention discloses a flow battery test platform, which comprises a flow battery system, a multi-physical field parameter coupling detection system and a data acquisition system, and is characterized in that the flow battery system comprises a flow battery and a visual clamp, and the flow battery comprises an electrode and a liquid storage tank; the visual clamp comprises a diaphragm, two graphite plates and two end plates, and at least one of the two end plates is a transparent end plate; the multi-physical field parameter coupling detection system comprises an optical detection unit, an electrolyte detection unit, a gas detection unit and a battery tester, wherein the optical detection unit is used for acquiring internal image data of the flow battery; the electrolyte detection unit is used for acquiring concentration data of the electrolyte; the gas detection unit is used for acquiring gas concentration data; the battery tester is used for charging and discharging the flow battery; and the data acquisition system is used for acquiring key characteristic data according to the image data, the concentration data of the electrolyte and the concentration data of the gas so as to adjust the running state of the battery.

Description

[0001] This application is a divisional application of the invention patent application with the application date of October 22, 2024, the Chinese application number 202411477732.X, and the invention name “Liquid Flow Battery Testing Platform”. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a liquid flow battery testing platform. Background Art

[0003] Liquid flow batteries generally use electrochemical redox reactions to achieve charging and discharging, so liquid flow batteries are a new type of large-scale electrochemical energy storage battery. It is different from batteries that usually use solid material electrodes or gas electrodes. Its active material is a flowing electrolyte solution, and the positive and negative electrolytes are circulated separately. Its most notable feature is large-scale power storage and the power and capacity can be designed independently. It has the characteristics of high capacity, wide application field, and long cycle life.

[0004] In order to reveal the complex reaction mechanism of liquid flow batteries, the PNNL laboratory in the United States has developed a liquid flow battery X-ray tomography imaging system, which realizes the non-destructive reconstruction of the three-dimensional microstructure inside the electrode and quantitatively analyzes the influence of geometric parameters such as porosity and specific surface area on mass transfer behavior. The Fraunhofer Institute in Germany used neutron scattering technology to reveal the distribution of electrolyte inside the carbon felt electrode and its correlation with current density. Hydrogenics in Canada has developed an online infrared thermal imaging system to achieve real-time monitoring and hot spot diagnosis of the temperature distribution inside the VRFB stack. However, the above-mentioned test platform is mainly aimed at offline multi-physical field detection or single physical field online detection, and it is impossible to obtain the coupling effects and dynamic laws between different physical fields during the charge and discharge process of the liquid flow battery in real time, so it is impossible to achieve integrated in-situ characterization and real-time monitoring of the multi-physical field characteristics of the liquid flow battery.

[0005] Therefore, how to provide a testing platform that can realize integrated in-situ characterization and real-time monitoring of the multi-physical field characteristics of flow batteries is an urgent problem to be solved. Summary of the invention

[0006] The present application provides a liquid flow battery testing platform, aiming to provide a testing platform capable of realizing integrated in-situ characterization and real-time monitoring of the multi-physical field characteristics of the liquid flow battery.

[0007] On the one hand, an embodiment of the present application provides a liquid flow battery testing platform, including a liquid flow battery system, a multi-physical field parameter coupling detection system and a data acquisition system; the liquid flow battery system includes: a liquid flow battery and a visualization fixture, the liquid flow battery includes an electrode and a liquid storage tank, the electrode includes a positive electrode and a negative electrode arranged in a stacked manner, and the liquid storage tank includes a positive electrode liquid storage tank and a negative electrode liquid storage tank arranged on both sides of the electrode; the visualization fixture includes a diaphragm, two graphite plates and two end plates, the diaphragm is arranged between the positive electrode and the negative electrode, the two graphite plates are arranged on the opposite sides of the electrode away from the diaphragm, and the two end plates are arranged on the opposite sides of the graphite plates away from the electrode, wherein at least one of the two end plates is a transparent end plate; the multi-physical field parameter coupling detection system includes: an optical detection unit, an electrolyte detection unit element, a gas detection unit and a battery tester, the optical detection unit is used to collect the internal image of the liquid flow battery in real time to obtain the internal image data of the liquid flow battery; the electrolyte detection unit is used to collect the electrolyte in the liquid storage tank in real time through a micro-sampling circuit to obtain the concentration data of the electrolyte; the gas detection unit is used to collect the gas in the liquid storage tank in real time to obtain the concentration data of the gas; the battery tester is used to charge and discharge the liquid flow battery and collect electrochemical data; the data acquisition system is used to obtain key feature data according to the image data, the concentration data of the electrolyte and the concentration data of the gas, and calculate the corresponding deviation value according to the mapping relationship between the key feature data and the preset performance indicators of the liquid flow battery, so as to adjust the operating state of the liquid flow battery according to the deviation value.

[0008] Optionally, in some embodiments of the present application, the end plate close to the optical detection unit is a transparent end plate, and the material used for the transparent end plate includes polymethyl methacrylate.

[0009] Optionally, in some embodiments of the present application, a plurality of spaced-apart flow channels are provided on one side of the graphite plate close to the electrode, and the flow channels are used to guide the electrolyte in the liquid storage tank to flow on the surface of the electrode.

[0010] Optionally, in some embodiments of the present application, the optical detection unit includes an optical microscope or a high-speed camera, and the image data includes at least one of flow parameters of the electrolyte in the flow channel, characteristic parameters of side reaction bubbles, and characteristic parameters of the electrode surface.

[0011] Optionally, in some embodiments of the present application, the electrolyte detection unit includes an in-situ ultraviolet spectrometer, and the concentration data of the electrolyte includes curve data of the concentration of anions and cations in the electrolyte changing with time.

[0012] Optionally, in some embodiments of the present application, the components of the electrolyte include tracer particles or fluorescent substances.

[0013] Optionally, in some embodiments of the present application, the gas detection unit includes an in-situ gas chromatograph, and the gas concentration data includes type data of gases released during the operation of the liquid flow battery and curve data of the concentration of each gas changing with time.

[0014] Optionally, in some embodiments of the present application, the material used for the electrode includes carbon felt or carbon cloth.

[0015] Optionally, in some embodiments of the present application, the key characteristic data include at least active material concentration, ion crossover degree, hydrogen evolution rate, Coulomb efficiency, energy efficiency and capacity decay rate.

[0016] Optionally, in some embodiments of the present application, the liquid flow battery system also includes a flow control unit, an electronic control unit and a temperature control unit, the flow control unit is used to control the electrolyte flow of the liquid flow battery, the electronic control unit is used to control the charge and discharge current density of the liquid flow battery, and the temperature control unit is used to control the temperature of the liquid flow battery; the battery tester is connected to the flow control unit, the electronic control unit and the temperature control unit, and the battery tester is also used to collect the deviation value corresponding to the parameter characteristic data output by the data acquisition system in real time and output it to the liquid flow battery system to adjust at least one of the electrolyte flow, charge and discharge current density and temperature of the liquid flow battery.

[0017] The liquid flow battery testing platform provided in the present application integrates a liquid flow battery system, a multi-physical field parameter coupling detection system and a data acquisition system, wherein the liquid flow battery system includes: a liquid flow battery and a visualization fixture, the liquid flow battery includes an electrode and a liquid storage tank, the electrode includes a positive electrode and a negative electrode arranged in a stacked manner, and the liquid storage tank includes a positive electrode liquid storage tank and a negative electrode liquid storage tank arranged on both sides of the electrode; the visualization fixture includes a diaphragm, two graphite plates and two end plates, the diaphragm is arranged between the positive electrode and the negative electrode, the two graphite plates are arranged on the opposite sides of the electrode away from the diaphragm, and the two end plates are arranged on the opposite sides of the graphite plates away from the electrode, wherein at least one of the two end plates is a transparent end plate; the multi-physical field parameter coupling detection system includes: an optical detection unit, an electrolyte detection unit, A gas detection unit and a battery tester, wherein the optical detection unit is used to collect the internal image of the liquid flow battery in real time to obtain the internal image data of the liquid flow battery; the electrolyte detection unit is used to collect the electrolyte in the liquid storage tank in real time through a micro-sampling circuit to obtain the concentration data of the electrolyte; the gas detection unit is used to collect the gas in the liquid storage tank in real time to obtain the concentration data of the gas; the battery tester is used to charge and discharge the liquid flow battery and collect electrochemical data; the data acquisition system is used to obtain key feature data based on the image data, the concentration data of the electrolyte and the concentration data of the gas, and calculate the corresponding deviation value based on the mapping relationship between the key feature data and the preset performance indicators of the liquid flow battery, so as to adjust the operating state of the liquid flow battery according to the deviation value. That is, the liquid flow battery testing platform integrates multiple testing methods such as optics, electrochemistry, spectroscopy, chromatography, etc., and can simultaneously obtain multiple physical field information such as light field, electric field, flow field, concentration field, etc. during the charging and discharging process of the liquid flow battery. By comprehensively analyzing multi-source characterization data, the coupling effects and dynamic laws between different physical fields can be obtained, avoiding the limitations caused by a single characterization and realizing integrated in-situ characterization and real-time monitoring of the multi-physical field characteristics of the liquid flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a first schematic diagram of the flow battery testing platform provided by the present application;

[0019] Figure 2 is a schematic diagram of a visualization fixture and a flow battery provided in this application;

[0020] Figure 3 It is a second schematic diagram of the flow battery testing platform provided by the present application;

[0021] Figure 4 is a schematic diagram of flow fields at different battery voltages provided by the present application;

[0022] Figure 5 It is a schematic diagram of the absorbance of the mixed electrolyte provided by the present application under light of different wavelengths;

[0023] Figure 6 It is a schematic diagram of the relationship between the number of cycles, hydrogen evolution concentration and time of a liquid flow battery in the prior art;

[0024] Figure 7 It is a schematic diagram of the relationship between the number of cycles of a liquid flow battery and the volume of hydrogen in the prior art;

[0025] Figure 8 It is a curve diagram of the capacity and volume of hydrogen gas as a function of voltage provided by the present application;

[0026] Fig. 9 It is a schematic diagram of the relationship between battery capacity, cycle number and energy efficiency provided in this application;

[0027] Fig.10 It is a schematic diagram of the SOC-voltage curve of the charging model without hydrogen evolution reaction model and coupled hydrogen evolution reaction model provided in the present application;

[0028] Fig.11 It is a schematic diagram of the concentration distribution cloud map of hydrogen;

[0029] Fig.12 It is a schematic diagram of the overpotential distribution cloud diagram. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. The described technical solutions are only used to explain and illustrate the ideas of the present application and should not be regarded as limiting the protection scope of the present application.

[0031] The various embodiments provided in this application are similar, and features in different embodiments may be combined with each other.

[0032] like Figure 1 As shown, an embodiment of the present application provides a liquid flow battery testing platform 100 , including a liquid flow battery system 10 , a multi-physical field parameter coupling detection system 20 , and a data acquisition system 30 .

[0033] In an embodiment of the present application, the flow battery system 10 includes: a flow battery 11 and a visualization fixture 12. The flow battery 11 includes an electrode 111 and a liquid storage tank 112, the electrode 111 includes a positive electrode 111 and a negative electrode 111 stacked, and the liquid storage tank 112 includes a positive electrode liquid storage tank 112 and a negative electrode liquid storage tank 112 arranged on both sides of the electrode 111.

[0034] like Figure 2As shown, the visualization fixture 12 includes a diaphragm 121, two graphite plates 122 and two end plates 123, the diaphragm 121 is arranged between the positive electrode 111 and the negative electrode 111, the two graphite plates 122 are arranged on the opposite sides of the electrode 111 away from the diaphragm 121, and the two end plates 123 are arranged on the opposite sides of the graphite plates 122 away from the electrode 111, wherein at least one of the two end plates 123 is a transparent end plate 123.

[0035] In an embodiment of the present application, the multi-physical field parameter coupling detection system 20 includes: an optical detection unit 21, an electrolyte detection unit 22, a gas detection unit 23 and a battery tester 24. The optical detection unit 21 is used to collect the internal image of the liquid flow battery 11 in real time to obtain the internal image data of the liquid flow battery 11. The electrolyte detection unit 22 is used to collect the electrolyte in the liquid storage tank 112 in real time through a micro-sampling circuit to obtain the concentration data of the electrolyte. The gas detection unit 23 is used to collect the gas in the liquid storage tank 112 in real time to obtain the concentration data of the gas. The battery tester 24 is used to charge and discharge the liquid flow battery 11 and collect electrochemical data.

[0036] In an embodiment of the present application, the data acquisition system is used to obtain key feature data based on image data, electrolyte concentration data, and gas concentration data, and calculate the corresponding deviation value based on the mapping relationship between the key feature data and the preset performance indicators of the liquid flow battery 11, so as to adjust the operating state of the battery according to the deviation value.

[0037] The liquid flow battery testing platform 100 provided in the present application integrates a liquid flow battery system 10, a multi-physical field parameter coupling detection system 20 and a data acquisition system 30, that is, the liquid flow battery testing platform 100 integrates multiple testing methods such as optics, electrochemistry, spectroscopy, chromatography, etc., and can synchronously obtain multiple physical field information such as light field, electric field, flow field, concentration field, etc. during the charging and discharging process of the liquid flow battery 11. By comprehensively analyzing multi-source characterization data, the coupling effects and dynamic laws between different physical fields are obtained, avoiding the limitations caused by a single characterization, and realizing a testing platform for integrated in-situ characterization and real-time monitoring of the multi-physical field characteristics of the liquid flow battery 11.

[0038] In the embodiment of the present application, the visualization fixture 12 is locked by bolts and nuts. The visualization fixture 12 is provided to solve the problem that the internal state of the flow battery 11 cannot be directly observed.

[0039] In the embodiment of the present application, a sealing groove is provided on the transparent end plate 123 to prevent leakage of the electrolyte.

[0040] In the embodiment of the present application, the material used for the transparent end plate 123 includes polymethyl methacrylate (PMMA for short). PMMA is a polymer organic glass with excellent optical properties and mechanical strength. In the visible light band, the transmittance of PMMA can be as high as 92% or more, which can ensure that the internal state of the battery is clearly visible. At the same time, PMMA material has good impact resistance and chemical corrosion resistance, which can meet the requirements of the battery operating environment.

[0041] In the embodiment of the present application, the graphite plate 122 is a composite bipolar plate, which has the dual functions of conducting electricity and conducting current. The graphite material has excellent electrical conductivity and can effectively collect the electrons generated on the surface of the electrode 111 and conduct them to the external circuit.

[0042] In an embodiment of the present application, a plurality of flow channels arranged at intervals are provided on one side of the graphite plate 122 close to the electrode 111, and the flow channels are used to guide the electrolyte in the liquid storage tank 112 to flow on the surface of the electrode 111. Specifically, the flow channel serves as a channel for the distribution and circulation of the electrolyte, guiding the electrolyte to flow evenly on the surface of the electrode 111 to ensure effective mass transfer of the active substance. The geometric parameters of the flow channel, such as width, depth, shape, etc., can be optimized and designed according to actual needs to achieve the best mass transfer effect. One side of the graphite plate 122 is tightly fitted with the electrode 111, and the other side is in contact with the transparent end plate 123.

[0043] In an embodiment of the present application, the material used for the electrode 111 includes carbon felt or carbon cloth. Specifically, the electrode 111 is made of porous carbon materials such as carbon felt and carbon cloth, and is responsible for providing a place for electrochemical reactions. The electrode 111 made of porous carbon material has a high specific surface area and excellent electrical conductivity, which can promote the contact and charge transfer between the electrolyte and the active substance. Among them, the thickness, porosity and other parameters of the electrode 111 can be optimized and selected according to the requirements of specific capacity, rate performance and so on. During the assembly process, the electrode 111 is placed between the graphite plate 122 and the transparent end plate 123, and is tightly fitted to the flow channel side of the graphite plate 122.

[0044] In the embodiment of the present application, the liquid flow battery system 10 further includes a flow control unit 13, an electric control unit 14 and a temperature control unit 15. The flow control unit 13 is used to control the electrolyte flow of the liquid flow battery 11, the electric control unit 14 is used to control the charge and discharge current density of the liquid flow battery 11, and the temperature control unit 15 is used to control the temperature of the liquid flow battery 11. The battery tester 24 is connected to the flow control unit 13, the electric control unit 14 and the temperature control unit 15. The battery tester 24 is also used to collect the deviation value corresponding to the parameter characteristic data output by the data acquisition system in real time and output it to the liquid flow battery system 10, so as to adjust at least one of the electrolyte flow, charge and discharge current density and temperature of the liquid flow battery 11.

[0045] In the embodiment of the present application, the optical detection unit 21 includes an optical microscope or a high-speed camera, and the image data includes at least one of the flow parameters of the electrolyte in the flow channel, the characteristic parameters of the side reaction bubbles, and the characteristic parameters of the surface of the electrode 111. Specifically, by using an optical microscope and / or a high-speed camera, a series of key information such as the flow state of the electrolyte in the flow channel, the nucleation and growth process of the side reaction bubbles, and the microscopic changes in the surface morphology of the electrode 111 are dynamically tracked and recorded, which provides valuable experimental data support for in-depth understanding of the reaction mechanism of the flow battery 11.

[0046] In the embodiments of the present application, visual observation is achieved through the optical detection unit 21 and the visualization fixture 12, so that parameters such as the size distribution, number density, and generation frequency of the side reaction bubbles can be quantitatively analyzed, and their impact on battery performance can be evaluated more comprehensively and systematically, providing an important basis for optimizing the structure of the electrode 111 and inhibiting the side effects of bubbles, revealing its evolution in long-term charge and discharge cycles, and clarifying the intrinsic mechanism of electrode 111 attenuation.

[0047] like Figure 3 As shown, the electrolyte detection unit 22 includes an in-situ ultraviolet spectrometer, and the electrolyte concentration data includes curve data of the concentration of anions and cations in the electrolyte changing with time.

[0048] In the embodiments of the present application, the electrolyte includes tracer particles or fluorescein. By adding tracer particles or fluorescein to the electrolyte and combining it with image velocimetry technology, the velocity field distribution in the flow channel can be accurately measured, and dead zones, bypasses and other areas that are not conducive to mass transfer can be identified, providing quantitative guidance for optimizing the flow field design.

[0049] Specifically, there is a phenomenon of mutual consumption between ions in the battery, which affects the battery capacity retention rate. In the past, the problem of electrolyte ion crossover and capacity decay was evaluated by observing the volume change in the liquid storage tank 112 and offline sampling, but this has the problem of electrolyte being oxidized during sampling and it is difficult to dynamically reflect the real situation inside the battery, which limits the in-depth understanding of its ion crossover and performance capacity decay mechanism.

[0050] In the embodiment of the present application, an in-situ UV spectrometer is combined with an optical visualization technique. Specifically, by introducing a micro-sampling loop into the liquid storage tank 112 of the flow battery system 10, the electrolyte sample is introduced into the in-situ UV spectrometer in real time. Figure 3As shown. Because of its analysis method based on electronic transition, the selective absorption of ultraviolet-visible light by electrons in molecules when they transition between different energy levels is used to obtain a spectrum of absorbance changing with wavelength, thereby realizing qualitative and quantitative analysis of the composition and content of the substance, and obtaining a curve of the change of anion and cation concentrations over time, and quantitatively evaluating the ion crossover rate and its correlation with battery capacity decay. At the same time, the introduction of the visualization fixture 12 can directly observe the permeation of the electrolyte on the membrane side, and the combination of fluorescent substances or tracer substances can more intuitively reflect the cross-permeation phenomenon of ions. Analyzing from the perspective of the combination of fluid field and electrochemical field can more accurately evaluate the kinetic process of ion crossover and reveal its intrinsic connection with battery capacity decay.

[0051] Since gas will be precipitated during the operation of the liquid flow battery 11, the formation of bubbles due to gas escape will affect the volume of the electrolyte and reduce the active surface area available for electrochemical reactions. This situation hinders the effective utilization of the electrode 111, resulting in a decrease in mass and charge transfer rate. Therefore, concentration polarization and ohmic polarization problems arise. Secondly, the gas evolution side reaction competes with the normal chemical reaction in the liquid flow battery 11, resulting in a decrease in the battery charging current. Therefore, after many cycles, the coulombic efficiency, energy efficiency, capacity retention rate and other performance indicators all decrease. In addition, due to the significant potential difference between the positive and negative half-cells during operation, the impact of the hydrogen and oxygen evolution side reactions becomes more obvious at the end of the charging process. Therefore, real-time detection of the gas evolution state is particularly important.

[0052] In an embodiment of the present application, the gas detection unit 23 includes an in-situ gas chromatograph, and the gas concentration data includes data on the types of gases released during battery operation and curve data on the concentration of each gas changing with time.

[0053] In an embodiment of the present application, an in-situ gas chromatograph and an optical visualization technique are combined. Specifically, by introducing the gas in the liquid storage tank 112 into the gas chromatograph in real time, using the different order of adsorption of different gases by the gas chromatograph, and then qualitatively and quantitatively analyzing the gas components, the concentration-time curves of byproducts such as hydrogen and oxygen are obtained, and the real-time occurrence rate of the side reaction is calculated accordingly. At the same time, by using a visualization fixture 12, it is possible to compare the differences in bubble behavior under different electrode 111 materials, surface structures, and flow field designs through quantitative analysis of bubble morphology parameters (such as diameter, contact angle, coverage, etc.), reveal its association with side reactions, and provide design ideas for suppressing bubbles and enhancing mass transfer. Furthermore, the bubble signal observed by visualization is matched with the concentration of byproducts detected by the chromatogram, and a quantitative relationship between bubble behavior and side reaction dynamics is established to form the spatiotemporal law of bubble evolution.

[0054] In an embodiment of the present application, the data acquisition system 30 is used to charge and discharge the visualization fixture 12 in the battery tester 24, and after obtaining image data such as the porous electrode 111, electrolyte flow, bubble behavior, etc. inside the battery through a microscope, the obtained image is enhanced, segmented, and feature extracted using a digital image processing algorithm to obtain the porosity, specific surface area, and liquid saturation of the porous electrode 111, and obtain the change patterns of the porosity, specific surface area, and liquid saturation with time and current density.

[0055] In an embodiment of the present application, the data acquisition system 30 is also used to perform in-situ ultraviolet spectroscopic testing inside the battery, measure the concentration changes of the electrolyte in real time, and continuously monitor the changes in the concentration and valence of active ions. It calculates the coulombic efficiency, energy efficiency, and self-discharge indicators of the battery, and obtains the spatial distribution of ion concentration by scanning and imaging different positions of the electrolyte, thereby obtaining charge transfer and cross-contamination degree data.

[0056] In the embodiment of the present application, the data acquisition system 30 is also used to calculate and process the obtained porosity, specific surface area, and liquid saturation data to obtain bubble characteristic data, and to calculate and process the obtained electrolyte ion concentration, charge transfer, and ion cross contamination degree data to obtain electrolyte ion cross signals. When the data acquisition system 30 detects the corresponding bubble characteristics or receives the electrolyte ion cross signal, it will start the in-situ gas chromatograph to monitor the gas components released during the battery operation, thereby obtaining the concentration data of gases such as hydrogen or oxygen in the liquid storage tank 112 of the liquid flow battery 11.

[0057] In the embodiment of the present application, the key characteristic data at least include active material concentration, ion crossover degree, hydrogen evolution rate, coulombic efficiency, energy efficiency and capacity decay rate. Specifically, the data acquisition system 30 is also used to collect the obtained electrolyte concentration data, gas concentration data, energy efficiency, coulombic efficiency and self-discharge rate, and then perform pre-processing operations such as cleaning, filtering and normalization to extract key characteristic parameters that can reflect battery performance, such as active material concentration, ion crossover degree, hydrogen evolution rate, coulombic efficiency, energy efficiency, capacity decay rate, etc.

[0058] Furthermore, the data acquisition system 30 compares the real-time data obtained by preprocessing with the initial value (such as: energy efficiency deviation = (real-time energy efficiency-initial energy efficiency) / initial energy efficiency×100%), calculates the deviation value, and then performs weighted average of indicators such as ion crossover degree, hydrogen evolution side reaction degree, energy efficiency deviation, coulomb efficiency deviation, and self-discharge rate (comprehensive score = ∑(indicator weight×indicator score) / ∑indicator weight), compares the comprehensive score with the set threshold, and gives a comprehensive score of the battery health status. When the evaluation result is lower than the preset threshold, a warning or alarm signal is issued in time. This is to achieve the diagnosis of the electrolyte ion concentration and the surface state of the electrode 111, and obtain the health status of the liquid flow battery system 10.

[0059] In the embodiment of the present application, the data acquisition system 30 is also used to establish a mapping relationship between performance indicators and key parameters, and to construct an evaluation system and prediction model for the performance of the liquid flow battery 11. Combined with the concentration data of the electrolyte monitored by the ultraviolet spectrometer and the ion crossover degree data and the concentration data of hydrogen monitored by the gas chromatograph, the health status of the battery is comprehensively evaluated, and the test analysis results are combined with the battery management system to realize online monitoring of the battery operating status, fault diagnosis, life prediction and other functions, and to dynamically adjust the battery pump speed, voltage window, current and other information in real time, forming a closed loop of data monitoring-data feedback-data mapping-data feedback-data monitoring to ensure the safe and efficient operation of the battery.

[0060] In the embodiments of the present application, Figure 1 As shown, the multi-physical field coupling effect acts together on the electrochemical field of the liquid flow battery 11 (such as the all-vanadium liquid flow battery 11), affecting the battery's performance parameters such as current, voltage, capacity, energy efficiency and coulomb efficiency. These data are summarized in the battery tester 24 and the electrochemical workstation through the data acquisition system 30. With the help of real-time feedback data, the flow control system, electrical control system and temperature control system of the liquid flow battery 11 can make corresponding adjustments in time to optimize the operating state of the battery. In this way, real-time online measurement of the multi-physical field coupling parameters of the liquid flow battery 11 is achieved.

[0061] As a specific implementation of the present application, taking the observation of hydrogen evolution side reaction of all-vanadium liquid flow battery as an example, the flow field area of ​​the liquid flow battery visualization fixture is 4cm×4cm, the flow channel width is 2mm, the depth is 2mm, a serpentine flow field is adopted, and the membrane is DuPont cation exchange membrane 211. At room temperature, 0.5mol / L VO is supplied to the negative electrode. 2+ solution (5mL / min), the positive electrode uses 0.5mol / L V 3+The battery electrochemical data were measured using an Arbin BT-2000 (Arbin Instruments) battery tester, and the optical data were obtained using a GP-680V electron microscope. The charging current was 200 mA cm -2 ,like Figure 4 As shown in the figure, from left to right are microscopic images of the flow field when the battery voltage is 1.5, 1.6, and 1.7V. When a side reaction occurs inside the battery to generate bubbles, it can be clearly observed that the bubbles will escape into the flow channel, and then according to the situation in the flow channel, it can be observed that the battery's hydrogen evolution voltage is 1.6V. Therefore, setting the battery's charging cutoff voltage to 1.6V will help avoid the occurrence of battery hydrogen evolution side reactions. This test can accurately quantify the battery's hydrogen evolution voltage and give the battery's recommended operating cutoff voltage.

[0062] In addition, when the charging current is 100mA·cm -2 Through further visualization experiments, it was found that hydrogen bubbles were generated only when the battery voltage was about 1.67V. Therefore, it was more appropriate to set the battery charging cut-off voltage to 1.67V at this current density. -2 When the battery voltage is about 1.56V, it is found through the visual observation experiment that the occurrence of hydrogen evolution reaction is observed. Therefore, at this current density, setting the battery charge cut-off voltage to 1.56V is conducive to avoiding the occurrence of long-cycle hydrogen evolution reaction. It should be pointed out that the voltage of hydrogen evolution is affected by many factors such as electrolyte state, temperature and charging current. In traditional charging and discharging devices, due to the lack of effective observation means, the battery charge cut-off voltage is uniformly set to 1.6V or 1.65V for charging and discharging. The root cause of this unscientific one-size-fits-all approach is that it is difficult to observe the battery state online, and the result will cause the capacity utilization rate of the electrolyte to be too low, increasing the electrolyte cost of the system. Or the depth of charging is too large, resulting in serious side reactions, thereby affecting the efficiency and life of the battery. It should be noted that the quantified parameters in this embodiment will provide quantified parameters for the establishment of relevant models, and the numerical membrane model containing hydrogen evolution is verified by experimental results.

[0063] As a specific implementation of the present application, taking the all-vanadium redox flow battery as an example, the Shimadzu UV2600 ultraviolet spectrophotometer is used to detect the ion crossover degree of the all-vanadium redox flow battery. Before the battery test, a series of V 3+ Concentrations from 0 to 50% of 0.1MV 3+ / VO 2+The mixed solution was used to measure the absorbance of solutions of different concentrations in the wavelength range of 300nm to 1100nm using an ultraviolet spectrophotometer. Subsequently, the all-vanadium redox flow battery was subjected to a charge and discharge test, and 1mL of electrolyte was sampled from the liquid storage tanks on both sides every cycle and sent to the ultraviolet spectrophotometer for testing.

[0064] like Figure 5 As shown, V 2+ The absorbance peak of the ion is around 550nm. 3+ The absorbance peak of ions is around 400nm, while VO 2+ The absorbance peak corresponds to a wavelength of about 760nm. As the charge and discharge proceed, the absorbance peak of the mixed electrolyte at 760nm gradually increases, while the absorbance peaks at 400 and 550nm gradually decrease, indicating that the ion valence is gradually shifting from 3.5 to 4. In addition, the higher the absorbance peak at 760nm, the more serious the degree of ion crossover.

[0065] Before the battery is operated, the volume of the positive and negative electrodes is 80 mL each. -2 After running for 200 cycles, the discharge capacity decreased from 1896mAh to 1086mAh. We found that the electrolyte volume on the negative electrode side decreased, while the electrolyte volume on the positive electrode side increased. Through volume detection, it was found that the negative electrode volume of the battery was 72mL and the positive electrode volume was 88mL. Through quantitative conversion of ultraviolet spectroscopy, the negative electrode V 3+ The concentration is 0.68 mol / L, V 2+ The concentration of 0.61mol / L, VO 2+ The concentration is 1.85 mol / L. According to the material conservation law of vanadium ions:

[0066]

[0067] Where V 0 (N) represents the volume of the negative electrode solution in the initial state, represents the concentration of vanadium ions on the negative electrode side in the initial state, V 0 (P) represents the volume of the positive electrode solution in the initial state, represents the concentration of vanadium ions on the positive electrode side in the initial state, V t (N) represents the volume of the negative electrode solution at time t, represents the concentration of vanadium ions on the negative electrode side at time t, V t (P) represents the volume of the positive electrode solution at time t, Represents the concentration of vanadium ions on the positive electrode side at time t.

[0068] You can get VO 2+The concentration is 0.1439mol / L. It was found that the concentration and volume of the active substances on the positive electrode side were higher than those on the negative electrode side, and at this time the capacity limit of the battery is determined by the negative electrode. Therefore, reducing the diffusion of active substances and volume at the negative electrode has become the main reason for the reduction in capacity. During the entire battery operation process, the volume, concentration, valence state and other information can be calculated through the data collected by the online testing platform built, and coupled with the online real-time changes in capacity. The theoretical capacity of the positive and negative electrodes calculated from multiple aspects such as volume, concentration, and valence state are analyzed and compared with the actual capacity of the battery to obtain the polarization information of the battery, and the capacity attenuation is diagnosed to accurately find the most critical parameters causing polarization and capacity attenuation, so as to make targeted improvements.

[0069] As a specific embodiment of the present application, taking the negative electrode side of the all-vanadium liquid flow battery as an example, an ultraviolet spectrophotometer is used to detect the change in the ion concentration of the battery in situ. The sampling device is placed in the negative electrode storage tank of the battery, and the all-vanadium liquid flow battery is subjected to charge and discharge tests, and 1 mL of electrolyte is sampled from the storage tank every 1 minute, and sent to the ultraviolet spectrophotometer for testing. After the test is completed, the electrolyte is pumped back into the storage tank. During the charging process, the peak absorbance of the electrolyte at a wavelength of 400nm gradually decreases, while the peak absorbance at a wavelength of 340nm gradually increases, indicating that the ion valence is gradually shifting from 3 valences to 2 valences. On the contrary, during the discharge process, the peak absorbance of the electrolyte at a wavelength of 400nm gradually increases, while the peak absorbance at a wavelength of 340nm gradually decreases, indicating that the ion valence is gradually shifting from 2 valences to 3 valences. In addition, the peak absorbance at a wavelength of 400nm during discharge is lower than the peak at the beginning of charging, reflecting the utilization rate of the electrolyte.

[0070] As a specific implementation of the present application, taking the hydrogen evolution side reaction on the negative electrode side of the all-vanadium liquid flow battery as an example, when the generation of bubbles is detected in the liquid flow battery visualization fixture using an optical microscope, 1 mL of gas is extracted from the liquid storage tank of the negative electrode of the battery using a Fuli GC9720Plus gas chromatograph. The gas chromatograph is used to qualitatively and quantitatively analyze the gas components based on the difference in the order of adsorption of different gases, focusing on observing the concentration of hydrogen at 0.2-0.25 min.

[0071] like Figure 6 As shown, at 200mA·cm -2The battery was run for 10 charge and discharge cycles under the following conditions, with the battery charge cutoff voltage set to 1.65V and the discharge cutoff voltage set to 0.9V. As the number of charge and discharge cycles of the battery increases, the peak value of hydrogen gradually increases, from the initial 0ppm to 253ppm, indicating that the concentration of hydrogen is gradually increasing. The occurrence of side reactions leads to the accumulation of hydrogen. In addition, by calculating the difference in hydrogen concentration between the two cycles and dividing it by the charge and discharge time of the battery, the average hydrogen production rate is calculated to be 25.3ppm, and this rate is used to evaluate the degree of occurrence of battery side reactions. Based on the measured hydrogen concentration of the liquid storage tank and the gas phase volume on the negative electrode side of the liquid storage tank, the hydrogen evolution current was tested online, and the amount of hydrogen in the system can be calculated. According to Faraday's law:

[0072] Q = nF,

[0073] Where n is the amount of hydrogen released; F is the Faraday constant, from which the amount of electricity Q corresponding to hydrogen release can be obtained, thereby calculating that the proportion of the charging current occupied by the hydrogen release current under the condition of 200 mA·cm-2 is approximately 0.1%.

[0074] In order to further explore the effect of cut-off voltage on the proportion of hydrogen evolution current, at 200 mA cm -2 The battery was run under the same conditions for 10 charge and discharge cycles. The battery charging cut-off voltage was set to 1.6V and the discharge cut-off voltage was set to 0.9V. The experimental results were analyzed and calculated to obtain that the proportion of the charging current occupied by the hydrogen evolution current was about 0.08%. Through online analysis, it can be seen that the cut-off voltage significantly affects the current of hydrogen evolution and its proportion. At the same time, in order to explore the effect of current density on the proportion of hydrogen evolution current, the battery was tested at 300mA·cm -2 The battery was run for 10 charge and discharge cycles under the same conditions, with the battery charge cut-off voltage set to 1.65V and the discharge cut-off voltage set to 0.9V. The experimental results were analyzed and calculated to show that the proportion of the charging current occupied by the hydrogen evolution current was about 0.14%. Through online analysis, it can be seen that the increase in current density can significantly affect the hydrogen evolution current and its proportion.

[0075] In addition, in order to explore the effect of the electrode on the hydrogen evolution current ratio, the -2 Under the conditions, 10 charge and discharge cycles were carried out using a carbon felt electrode loaded with bismuth particles, with the battery charge cut-off voltage set at 1.65V and the discharge cut-off voltage set at 0.9V. The experimental results were analyzed and calculated to obtain that the proportion of the charging current occupied by the hydrogen evolution current was about 0.02%. Through online analysis, it can be seen that the electrode modified with bismuth particles can significantly reduce the current of hydrogen evolution and its proportion.

[0076] Through our online platform, we can accurately analyze the hydrogen evolution current and some of its key influencing factors. Figure 6 and 7 It can be seen that the impact of hydrogen evolution on batteries in the past was only some qualitative analysis, but this system can obtain the real-time online quantitative reaction current of hydrogen evolution. The relationship between hydrogen evolution current and temperature, charge and discharge cut-off voltage, and flow rate can be analyzed through this online measurement platform.

[0077] As a specific implementation of the present application, taking the hydrogen evolution side reaction on the negative electrode side of the all-vanadium liquid flow battery as an example, the degree of the hydrogen evolution side reaction is detected in situ by using the multi-physical field parameter coupling of an electrochemical workstation-optical microscope-gas chromatograph-ultraviolet spectrophotometer. A gradient charge with an interval of 0.1V is set on the electrochemical workstation. When charged to the specified voltage, the gas chromatograph extracts 1mL of gas from the liquid storage tank at the negative electrode of the battery to perform a quantitative analysis of the hydrogen. At the same time, an optical microscope is used to detect the generation of bubbles in the liquid flow battery visualization fixture, and the number and volume of bubbles are calculated in parallel, such as Figure 8 shown.

[0078] In a single cycle, when the battery voltage is less than 1.8V, the concentration of hydrogen increases slowly and linearly; when the battery voltage is greater than 1.8V, the volume of hydrogen increases rapidly and exponentially, from 0.2mL to 24.8mL, and the number and volume of bubbles also increase rapidly with the concentration. At the same time, the change in ion concentration in the negative electrode storage tank is detected in situ using an ultraviolet spectrophotometer, and it can be found that the valence state has deviated. This shows that when the battery cut-off voltage is greater than 1.8V, the side reactions of the battery are very serious, which will seriously affect the performance of the battery and have a significant impact on the cycle stability of the battery.

[0079] As a specific implementation of this application, the all-vanadium liquid flow battery was used as the research object, and the internal capacity attenuation and side reaction degree of the battery during long-term operation at different flow rates were measured by using an electrochemical workstation, an optical microscope and a gas chromatograph. The flow field area was 4cm×4cm, the flow channel width was 2mm, the depth was 2mm, a serpentine flow field was used, and the membrane was DuPont cation exchange membrane 211. The experiment was carried out at room temperature, and 1M VO was supplied to the negative electrode. 2+ solution, the positive electrode uses 1M V 3+ The battery electrochemical data were measured and collected using an Arbin BT 2000 (Arbin Instruments) battery tester, and the optical data were collected using a GP-680V electron microscope, with the number of charge and discharge cycles set to 350.

[0080] In order to study the effect of different flow rates on battery performance, the flow rate gradient was set to 3, 5, and 9 mL min -1 cm -2 , and detect changes in battery capacity and gas concentration, such as Fig. 9As shown in the results, it can be seen that as the flow rate gradually increases from 3 mL min -1 cm -2 Increase to 5mL·min -1 cm -2 When the flow rate increases from 5 mL·min -1 cm -2 Increased to 9 mL·min -1 cm -2 When the battery is charged, the capacity decay of the battery gradually increases until 1.143mAh / cycle. At the same time, the gas generation rate shows that as the battery flow rate increases, the gas generation rate gradually slows down.

[0081] As a specific implementation of the present application, this embodiment collects online information such as hydrogen evolution overpotential, hydrogen evolution rate, electrolyte change state, etc. obtained by online measurement, performs multi-physics simulation on the battery charge and discharge state, and performs multiphase flow coupling on hydrogen generation in the model. By adding the side reaction effect and multiphase flow model, the model has a higher degree of fit and is closer to the actual operating state, such as Fig.10 As shown, by charging current of 300mA·cm -2 , flow rate 5mL·min -1 cm -2 Under the battery operating conditions, by comparing the SOC-voltage curves of the actual battery test, the charging model without hydrogen evolution reaction model and the charging model coupled with hydrogen evolution reaction model, it can be seen that the model coupled with hydrogen evolution reaction has a higher degree of fit with the actual battery test and is closer to the actual operation.

[0082] like Fig.11 and Fig.12 As shown in the figure, according to the hydrogen concentration distribution cloud map and the overpotential distribution cloud map, it can be seen that the overpotential under the ribs is lower, hydrogen evolution reaction is more likely to occur, and it is closer to the actual situation. This platform provides experimental online monitoring for the actual operation of the battery, which is beneficial to the health status detection of the battery and improves the performance of the battery.

[0083] As a specific implementation of the present application, this embodiment, based on the state of health observation, inhibits the occurrence of battery side reactions from multiple aspects of electrodes, diaphragms and operating parameters. For electrodes, 0.005 mol of bismuth nanoparticle catalyst is introduced and loaded on carbon felt electrodes; for diaphragms, 0.003 mol of SiO2 nanoparticles are added to the surface of the negative electrode side to block the diffusion of the solution and active substances on the negative electrode side; in terms of flow rate, the flow rate is maintained at 6 mL min in the early stage. -1 cm -2At the end of charging, the flow rate was increased to 9 mL min -1 cm -2 After testing, the improved battery capacity retention rate increased from 36% to 86%, and the energy efficiency increased from 76% to 88%. This shows that after understanding the relationship between online parameters and performance, targeted improvements can greatly improve battery performance, further illustrating the importance of the online parameter acquisition platform and health status detection for flow batteries.

[0084] A liquid flow battery testing platform inputted in the embodiment of the present application is introduced in detail above. The description of the above embodiment is only used to help understand the core idea of ​​the present application, and the above description should not be understood as limiting the protection scope of the present application.

Claims

1. A flow battery testing platform, characterized in that: Including liquid flow battery system, multi-physics field parameter coupling detection system and data acquisition system; The liquid flow battery system comprises: A liquid flow battery comprises an electrode and a liquid storage tank, wherein the electrode comprises a positive electrode and a negative electrode arranged in a stacked manner, and the liquid storage tank comprises a positive electrode liquid storage tank and a negative electrode liquid storage tank arranged on both sides of the electrode; A visualization fixture for observing the internal state of the flow battery; The multi-physical field parameter coupling detection system is used to synchronously acquire internal image data of the flow battery, concentration data of the electrolyte, concentration data of the gas, and electrochemical data of the flow battery; The data acquisition system is used to obtain key feature data based on the image data, the concentration data of the electrolyte and the concentration data of the gas, and calculate the corresponding deviation value based on the mapping relationship between the key feature data and the preset performance indicators of the liquid flow battery, so as to adjust the operating state of the liquid flow battery according to the deviation value.

2. The flow battery testing platform according to claim 1, characterized in that: The electrolyte detection unit includes an in-situ ultraviolet spectrometer, and the electrolyte concentration data includes curve data of changes in concentrations of anions and cations in the electrolyte over time.

3. The flow battery testing platform according to claim 2, characterized in that: The data acquisition system is also used to perform in-situ ultraviolet spectroscopic testing inside the battery, measure the concentration changes of the electrolyte in real time, and continuously monitor the changes in the concentration and valence of active ions, calculate the coulombic efficiency, energy efficiency, and self-discharge indicators of the battery, and obtain the spatial distribution of ion concentration by scanning and imaging different positions of the electrolyte, and obtain charge transfer and cross-contamination degree data.

4. The flow battery testing platform according to claim 1, characterized in that: The electrolyte solution includes tracer particles or fluorescent substances.

5. The flow battery testing platform according to claim 1, characterized in that: The gas detection unit includes an in-situ gas chromatograph, and the gas concentration data includes type data of gases released during the operation of the liquid flow battery and curve data of the concentration of each gas changing with time.

6. The flow battery testing platform according to claim 1, characterized in that: The key characteristic data at least include active material concentration, ion crossover degree, hydrogen evolution rate, coulomb efficiency, energy efficiency and capacity decay rate.

7. The flow battery testing platform according to claim 1, characterized in that: The liquid flow battery system further includes a flow control unit, an electric control unit and a temperature control unit, wherein the flow control unit is used to control the electrolyte flow of the liquid flow battery, the electric control unit is used to control the charge and discharge current density of the liquid flow battery, and the temperature control unit is used to control the temperature of the liquid flow battery; The battery tester is connected to the flow control unit, the electronic control unit and the temperature control unit. The battery tester is also used to collect the deviation value corresponding to the parameter characteristic data output by the data acquisition system in real time and output it to the liquid flow battery system to adjust at least one of the electrolyte flow, charge and discharge current density and temperature of the liquid flow battery.

8. The flow battery testing platform according to claim 1, characterized in that: The multi-physical field parameter coupling detection system comprises: An optical detection unit, used for collecting an internal image of the liquid flow battery in real time to obtain internal image data of the liquid flow battery; An electrolyte detection unit, used to collect electrolyte in the liquid storage tank in real time through a micro-sampling circuit to obtain concentration data of the electrolyte; A gas detection unit, used to collect the gas in the liquid storage tank in real time to obtain the concentration data of the gas; A battery tester is used to charge and discharge the liquid flow battery and collect electrochemical data.

9. The flow battery testing platform according to claim 8, characterized in that: Visual observation is achieved through an optical detection unit and a visualization fixture, and quantitative analysis includes at least one parameter of the size distribution, number density, and generation frequency of the side reaction bubbles.

10. The flow battery testing platform according to claim 8 or 9, characterized in that: The visualization fixture includes a diaphragm, two graphite plates and two end plates, wherein the diaphragm is arranged between the positive electrode and the negative electrode, the two graphite plates are arranged on opposite sides of the electrode away from the diaphragm, and the two end plates are arranged on opposite sides of the graphite plates away from the electrode, wherein at least one of the two end plates is a transparent end plate.

Images