A cross-validated iron-chromium flow battery asymmetric polarization data decoupling system and method

Abstract

The application provides a cross-verification iron-chromium flow battery asymmetric polarization data decoupling system and method, and belongs to the technical field of electrochemical testing of redox flow batteries.The system comprises a main operation module, a polarization decoupling module, a test module, a control module and a data analysis module.The core technical problem to be solved by the application is how to measure and separate, in a line, synchronization and high-precision manner, the ohmic polarization, activation polarization and concentration difference polarization contributions of four independent half-cell reactions, namely the oxidation of divalent iron and the reduction of trivalent iron at the positive electrode and the oxidation of divalent chromium and the reduction of trivalent chromium at the negative electrode of the iron-chromium flow battery under actual operation conditions, and establish a reliable internal cross-verification mechanism to ensure the accuracy of the decoupling results.

Description

Technical Field

[0001] This invention relates to the field of electrochemical testing technology for redox flow batteries, and in particular to a cross-validation system and method for decoupling asymmetric polarization data of iron-chromium flow batteries. Background Technology

[0002] Despite its promising future, the path from laboratory research to large-scale commercial application of iron-chromium flow batteries still faces a series of technical bottlenecks that urgently need to be overcome. These bottlenecks directly restrict the improvement of energy efficiency, power density, and long-term operational stability, constituting major obstacles in the industrialization process. One particularly prominent challenge stems from the hydrogen evolution side reaction at the negative electrode. Because the reduction potential of trivalent chromium ions is very close to the hydrogen evolution potential of hydrogen ions on commonly used carbon-based electrodes (such as carbon cloth), during charging, especially in areas with high state of charge or high local overpotential on the electrode surface, the hydrogen evolution reaction will interact with the target reaction (Cr). 3+ Reduced to Cr 2+ The hydrogen evolution reaction (SOC) leads to competition for energy. This side reaction is not simply a loss of current; it triggers a series of negative effects: First, it directly consumes electrons and hydrogen ions in the electrolyte that should be used to store chemical energy, causing a gradual imbalance in the state of charge (SOC) of the positive and negative electrode electrolytes. Over time, during discharge, the total amount of divalent chromium that can be oxidized at the negative electrode will be less than the total amount of trivalent iron that needs to be reduced at the positive electrode, causing a continuous accumulation of trivalent iron in the positive electrode electrolyte, ultimately leading to irreversible capacity decay of the battery. Second, the hydrogen evolution reaction severely reduces the overall efficiency of the battery. On the one hand, the current used to generate hydrogen does not contribute to energy storage, directly leading to a decrease in coulombic efficiency; on the other hand, the continuous consumption of hydrogen ions will change the electrolyte composition, potentially reducing its conductivity and thus increasing ohmic polarization. At the same time, the SOC imbalance exacerbates the concentration difference between the positive and negative electrode electrolytes, further increasing concentration polarization. Even more challenging is that hydrogen bubbles generated on the electrode surface can cover some active sites, hindering the mass transfer process between reactants and products. This, in turn, worsens activation polarization and concentration polarization to varying degrees, leading to a significant reduction in voltage efficiency.

[0003] Besides the hydrogen evolution problem, the iron-chromium redox flow battery system also faces complex and highly asymmetric electrochemical reaction kinetics, which is another core challenge for improving its performance. Specifically, the Fe at the cathode... 3+ / Fe 2+ The redox couple exhibits near-ideal reversibility, with both oxidation and reduction reactions showing rapid kinetic rates and good symmetry. Therefore, in conventional analysis, the activation polarization values ​​during charging and discharging can be approximated as equal. However, the Cr at the negative electrode... 3+ / Cr 2+The redox couples exhibit drastically different behaviors, with inherent and severe asymmetries in their kinetic processes. The oxidation of divalent chromium to trivalent chromium is thermodynamically highly spontaneous, even occurring rapidly in air; conversely, the reduction of trivalent chromium to divalent chromium, due to its high activation energy barrier, is not thermodynamically spontaneous and requires external voltage or other forced conditions. This slow kinetics of the negative electrode reduction reaction has become one of the main bottlenecks limiting the overall power performance and energy efficiency of iron-chromium flow batteries. A direct consequence is that the activation polarization value of the negative electrode differs significantly between charging (reduction) and discharging (oxidation) processes, completely invalidating the traditional assumption of "symmetrical activation polarization between positive and negative electrodes." How to accurately measure and separate this inherent, asymmetric activation polarization experimentally remains a crucial unresolved scientific problem in this field.

[0004] A deeper exploration of the intrinsic mechanisms of battery performance degradation reveals that while its external manifestation is a decrease in capacity and voltage efficiency, its underlying electrochemical root cause can often be traced back to the exacerbation of various polarization phenomena. Polarization is the phenomenon where the actual battery potential deviates from its thermodynamic equilibrium potential. Total polarization is generally decomposed into three parts: activation polarization, ohmic polarization, and concentration polarization. Activation polarization originates from the activation energy barrier that the electrochemical reaction itself needs to overcome and is closely related to the activity of the electrode catalyst and the state of the electrode surface. Ohmic polarization is caused by the resistance encountered by electrons and ions during transport in various battery components (electrodes, electrolyte, separator, etc.). Concentration polarization is caused by the difference between the concentration of reactants on the electrode surface and the concentration in the bulk electrolyte and is closely related to the mass transfer characteristics of the system. In actual operation, catalyst deactivation and electrode contamination increase activation polarization; membrane blockage and aging, decreased electrolyte conductivity, and increased contact resistance increase ohmic polarization; while electrolyte component imbalance, uneven ion distribution, or flow channel blockage exacerbate concentration polarization. These three polarizations are coupled together, jointly determining the battery's operating voltage and energy loss. Therefore, accurate analysis and decoupling of the total polarization, and quantitative assessment of the contribution of each polarization, becomes a crucial "lens" for diagnosing battery performance degradation and identifying technological bottlenecks. Based on accurate polarization decoupling results, key kinetic and mass transfer parameters such as exchange current density, reaction rate constant, and ion diffusion coefficient can be further calculated. These parameters are core inputs for constructing high-fidelity electrochemical models, accurately estimating the battery's state of charge (SOC) and state of health (SOH), and performing system-level design and operational optimization. Therefore, developing a method to accurately obtain information on each polarization component of an iron-chromium redox flow battery is of paramount importance for its material development, structural design, state management, and performance optimization.

[0005] Faced with the common need for polarization decoupling, existing technical solutions fall short when applied to iron-chromium redox flow batteries, revealing significant limitations. For example, Chinese patent application number 201910826102.1 discloses a method for testing the reaction kinetic parameters of porous electrodes in flow batteries. The core calculation premise of this method is that the activation polarization values ​​of the positive and negative electrodes must first be obtained. Based on this, it constructs a symmetrical battery, subtracts the calculated ohmic polarization and concentration polarization from the total polarization voltage to obtain the total activation polarization, and further allocates the contribution of the two electrodes based on the assumption that "the activation polarization of the positive and negative electrodes is equal." However, this method has a key limitation when applied to iron-chromium redox flow battery systems: its core assumption of "activation polarization symmetry" is seriously inconsistent with the aforementioned asymmetric characteristics of the negative electrode reaction kinetics of iron-chromium batteries. Although the academic community has used theoretical calculations and spectroscopic methods to study the Cr... 3+ / Cr 2+ While beneficial explorations have been made into the coordination environment and reaction pathway, a universal method that can directly and reliably separate and mutually verify this asymmetric activation polarization is still lacking at the experimental measurement level.

[0006] In summary, current technological advancements in the field of iron-chromium redox flow batteries (FCRBs) suffer from a significant mismatch between analytical methods and the specific characteristics of the battery. The lack of a scientifically sound and universally applicable testing and analytical method to decouple and verify the contribution of asymmetric activation polarization severely hinders a deep understanding of the battery's performance degradation mechanism and restricts the precise control of optimization directions for its key materials and components. Therefore, developing a polarization analysis and verification method that overcomes the limitations of existing methods and is specifically applicable to the complex and asymmetric electrochemical system of iron-chromium redox flow batteries has become an indispensable and crucial step in promoting the maturity of this technology. Summary of the Invention

[0007] This invention provides a cross-validated decoupling system and method for asymmetric polarization data in iron-chromium flow batteries. The core technical problem to be solved is how to measure and separate the ohmic polarization, activation polarization, and concentration polarization contributions of the four independent half-cell reactions—the oxidation of ferrous iron and the reduction of ferric iron at the positive electrode, and the oxidation of chromium divalent and the reduction of chromium trivalent at the negative electrode—under actual operating conditions in an iron-chromium flow battery, in a reliable manner, and to establish a reliable internal cross-validation mechanism to ensure the accuracy of the decoupling results.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A cross-validated asymmetric polarization data decoupling system for iron-chromium flow batteries includes: The main operating module includes a rechargeable battery, a positive electrode liquid tank, a negative electrode liquid tank, an electrolyte circulation pipeline, and a pump and valve assembly. The positive electrode chamber of the rechargeable battery is connected to the positive electrode liquid tank, and the negative electrode chamber of the rechargeable battery is connected to the negative electrode liquid tank, all through the electrolyte circulation pipeline. The pump and valve assembly is installed on the electrolyte circulation pipeline and is used to drive the electrolyte to circulate within the pipeline. The polarization decoupling module, connected in parallel with the electrolyte circulation pipeline of the main operating module, includes three test cells: a positive electrode-side symmetrical cell, a negative electrode-side symmetrical cell, and a positive and negative electrode polarization acquisition cell. Both chambers of the positive electrode-side symmetrical cell are connected to the electrolyte circulation pipeline corresponding to the positive electrode tank, and both chambers of the negative electrode-side symmetrical cell are connected to the electrolyte circulation pipeline corresponding to the negative electrode tank. The positive electrode chamber of the positive and negative electrode polarization acquisition cell is connected to the electrolyte circulation pipeline corresponding to the positive electrode tank, and the negative electrode chamber is connected to the electrolyte circulation pipeline corresponding to the negative electrode tank, for synchronously outputting electrochemical signals from the three test cells. The testing module includes a charge / discharge instrument and an electrochemical workstation. The charge / discharge instrument is electrically connected to the charge / discharge battery and three test batteries, respectively, and is used to control the charge / discharge of the charge / discharge battery, output constant current charging excitation to the three test batteries, and acquire their steady-state voltage. The electrochemical workstation is electrically connected to the three test batteries, respectively, and is used to acquire the electrochemical impedance spectroscopy data and the constant current charging transient response voltage curve with millisecond time resolution for each battery. The control module is connected to the main operation module, polarization decoupling module and test module respectively. It is used to coordinate the control of electrolyte circulation and test timing, receive all data collected by the test module and transmit it to the data analysis module. The data analysis module, communicating with the control module, is used to decouple the total polarization, ohmic polarization, activation polarization, and concentration polarization of the four half-cell reactions based on the received steady-state voltage and electrochemical impedance spectroscopy data; it is used to perform relaxation time distribution analysis on the electrochemical impedance spectroscopy data to obtain the characteristic relaxation time constant; and it is used to calculate the polarization component values ​​for cross-validation and evaluate the accuracy of the decoupling results by combining the transient response voltage curve and the characteristic relaxation time constant; the four half-cell reactions are the positive electrode oxidation reaction of ferrous iron, the positive electrode reduction reaction of ferric iron, the negative electrode oxidation reaction of ferrous chromium, and the negative electrode reduction reaction of ferric chromium.

[0009] In this specification, the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the positive and negative electrode polarization acquisition battery adopt the same battery structure, and the electrode materials, proton exchange membranes, and flow channel structures are all kept the same.

[0010] In this specification, the electrochemical workstation uses a two-electrode testing mode to perform electrochemical impedance spectroscopy tests on three test cells. The tests are conducted during the steady-state phase of constant current charging of the corresponding cells.

[0011] In this specification, the control module switches the electrolyte flow path through a pump and valve matching device, so that the polarization decoupling module and the main operating module are in parallel synchronous operation or independent offline operation; the control module is also used to perform periodic intermittent tests on the three test batteries of the polarization decoupling module.

[0012] In this specification, the periodic intermittent test includes a testing phase and a settling phase. The testing phase lasts for 5 to 20 minutes, and the settling phase lasts for 1 to 30 minutes, to ensure that the electrolyte concentration gradient and electrode interface state return to a quasi-steady state before the next round of testing.

[0013] A cross-validated method for decoupling asymmetric polarization data of iron-chromium flow batteries, using the cross-validated iron-chromium flow battery asymmetric polarization data decoupling system described in any one of the above-mentioned methods, wherein the cross-validated method for decoupling asymmetric polarization data of iron-chromium flow batteries includes: S1. The control module drives the pump and valve device to synchronously circulate the positive electrolyte in the positive electrode chamber of the charge / discharge battery, the two chambers of the positive electrode side symmetrical battery, and the positive electrode chamber of the positive and negative polarization acquisition battery. At the same time, the negative electrolyte is synchronously circulated in the negative electrode chamber of the charge / discharge battery, the two chambers of the negative electrode side symmetrical battery, and the negative electrode chamber of the positive and negative polarization acquisition battery, forming a stable test condition. S2. Based on stable test conditions, the charge-discharge instrument is controlled by the control module to perform constant current charging on the three test batteries at the same current density as the charging and discharging batteries, and the steady-state voltage of each battery before and after charging is collected. The total polarization of each battery is calculated through the steady-state voltage. Simultaneously, the electrochemical workstation is controlled to perform electrochemical impedance spectroscopy tests on the three test batteries and collect the electrochemical impedance spectroscopy data of each battery. S3. Based on the electrochemical impedance spectroscopy data, the ohmic resistance and charge transfer resistance of each of the three test batteries are obtained by the data analysis module. Then, the total ohmic resistance and total charge transfer resistance of the positive and negative half-reactions of the positive electrode symmetrical battery, the negative electrode symmetrical battery, and the positive and negative electrode polarization acquisition battery are obtained by disassembling them respectively. S4. Based on total polarization, ohmic resistance, charge transfer resistance, total ohmic resistance and total charge transfer resistance, the ohmic polarization, activation polarization and concentration polarization of the three test cells are calculated by the data analysis module. S5. Ohmic polarization, activation polarization, and concentration polarization based on positive electrode side-symmetric cells, based on Fe 3+ / Fe 2+ The electrochemical reversibility of the redox couple was determined by setting the ohmic polarization and activation polarization of the reduction of ferric iron and the oxidation of ferrous iron in the symmetrical cell on the positive electrode side to be equal, thus obtaining the polarization reference value of a single positive electrode half-reaction. S6. Based on the positive and negative electrode polarization, the ohmic polarization, activation polarization, concentration polarization of the battery and the positive electrode half-reaction polarization reference value, the polarization value of the negative electrode trivalent chromium reduction reaction is calculated. S7. Based on the ohmic polarization, activation polarization, and concentration polarization of the negative electrode side-symmetric cell, as well as the polarization value of the negative electrode trivalent chromium reduction reaction, the polarization value of the negative electrode divalent chromium oxidation reaction is separated, and finally the ohmic polarization and activation polarization of the four half-cell reactions are decoupled.

[0014] In this specification, when the positive electrolyte in the positive electrode tank is at 50% charge, in S5, the concentration polarization of the trivalent iron reduction and divalent iron oxidation reactions in the symmetrical battery on the positive electrode side is further set to be equal. In S6, the concentration polarization of the trivalent chromium reduction reaction in the negative electrode is calculated simultaneously. In S7, the concentration polarization of the divalent chromium oxidation reaction in the negative electrode is separated simultaneously. Finally, the concentration polarization of the four half-cell reactions is decoupled and obtained.

[0015] This specification also includes a cross-validation step for the decoupling results, as detailed below: Based on electrochemical impedance spectroscopy data, relaxation time distribution analysis was performed through the data analysis module to obtain the characteristic relaxation time constants corresponding to activation polarization and concentration polarization of the three test cells. During the static setting phase of the polarization decoupling module, the electrochemical workstation is controlled by the control module to acquire the constant current charging transient response voltage curves of the three test batteries with millisecond time resolution. Based on the characteristic relaxation time constant and transient response voltage curve, the voltage value at the corresponding moment is extracted, and the polarization component value for cross-validation is calculated. The cross-validation polarization component value is compared with the corresponding polarization value. If the deviation between the two is within the preset tolerance range, the decoupling result is confirmed to be valid; otherwise, a verification failure message is output.

[0016] In this specification, the transient response voltage curve used to calculate the polarization component values ​​for cross-validation is replaced with the open-circuit voltage relaxation curve with millisecond-level time resolution, which is collected starting when the constant current charging of the three test batteries stops.

[0017] In this manual, in step S2, when the voltage fluctuation amplitude is within the preset threshold and the duration is not less than 30 seconds, it is determined that a steady state has been reached and the corresponding voltage data is collected; the execution sequence of constant current charging test and electrochemical impedance spectroscopy test is as follows: after the constant current charging test reaches a steady state, the electrochemical impedance spectroscopy test is executed immediately to ensure that the two sets of test data correspond to the same operating conditions.

[0018] In summary, the present invention has at least the following beneficial effects: (1) Unprecedented depth of analysis: For the first time, the polarization of the four independent half-cell reactions (not just the positive and negative electrodes) of the iron-chromium flow battery was completely decoupled, providing the most direct and detailed experimental data for a deeper understanding of the complex asymmetric electrochemical behavior inside the battery.

[0019] (2) High precision and high reliability: The original cross-validation mechanism combines the frequency domain analysis method based on steady state / EIS with the time domain analysis method based on transient voltage curves with millisecond-level time resolution. The measurement results of the two physical principles corroborate each other, which greatly improves the credibility and accuracy of the final decoupled data.

[0020] (3) Online synchronous monitoring: The polarization decoupling module is connected in parallel with the main operating battery and uses the same electrolyte, which ensures a high degree of consistency between the test conditions and the actual working conditions, realizes true online and real-time diagnosis, and overcomes the lag and distortion problems of traditional offline test methods.

[0021] (4) Non-invasive measurement: The entire measurement process does not require the implantation of any probe or reference electrode inside the main battery, and will not interfere with the normal operation of the main battery and the integrity of its internal structure, thus ensuring the non-destructive nature and long-term applicability of the measurement.

[0022] (5) The system design is ingenious and practical: by combining three micro-batteries with identical structures, a solvable "electrochemical equation set" is cleverly constructed. The design concept is clear and easy to implement and integrate in engineering. The design of the periodic intermittent testing mode achieves a good balance between ensuring data quality and reducing system energy consumption.

[0023] (6) Significant application value: The high-precision decoupling data obtained by this invention can be directly used for: ①Performance bottleneck diagnosis: Accurately identify the key factors limiting battery performance, providing clear guidance for the optimization of electrode materials, catalysts, and electrolyte formulations.

[0024] ② Advanced BMS Development: Provides core parameters for establishing a high-fidelity battery internal state model, significantly improving the accuracy of BMS in estimating SOC, SOH, and SOP.

[0025] ③ Intelligent operation control: Based on real-time insight into the internal polarization state, closed-loop optimization control of battery operating parameters (such as current and flow rate) can be achieved, thereby maximizing operating efficiency and lifespan while ensuring safety.

[0026] ④ Fault early warning and diagnosis: By monitoring the evolution trend of each polarization component over a long period of time, early fault characteristics such as hydrogen evolution, electrode passivation, and membrane fouling can be identified in advance, enabling predictive maintenance. Attached Figure Description

[0027] Figure 1 A schematic diagram of an asymmetric polarization data decoupling system for cross-validation of an iron-chromium flow battery.

[0028] Figure 2 A schematic diagram of the decoupling method for asymmetric polarization data in iron-chromium flow batteries for cross-validation.

[0029] Figure 3 A schematic diagram of the electrochemical impedance spectroscopy (Nyquist plot) of the battery under specific operating conditions and the fitting results of its equivalent circuit, obtained for positive and negative electrode polarization.

[0030] Figure 4 This is a schematic diagram illustrating the polarization decoupling results of the battery under different SOCs for collecting data on positive and negative electrode polarization.

[0031] Figure 5 A schematic diagram showing the relationship between ohmic polarization and activation polarization and state of charge (SOC) during the charging and discharging of a battery, corresponding to three typical electrochemical reactions.

[0032] Figure 6 This is a schematic diagram of the cross-validation mechanism.

[0033] Figure 7 for Figure 3 A schematic diagram of the DRT analysis results of the Nyquist plot.

[0034] Figure 8 This is a schematic diagram of the transient response voltage curve of constant current charging with millisecond-level time resolution for a symmetrical battery on the positive electrode side when the SOC of the positive electrode electrolyte is 100%. Detailed Implementation

[0035] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0036] This embodiment provides a cross-validated asymmetric polarization data decoupling system for iron-chromium flow batteries, including: The main operating module includes a charge / discharge battery 101, a positive electrode liquid tank 102, a negative electrode liquid tank 103, an electrolyte circulation pipeline, and a pump and valve assembly. The positive electrode chamber of the charge / discharge battery 101 is connected to the positive electrode liquid tank 102, and the negative electrode chamber of the charge / discharge battery 101 is connected to the negative electrode liquid tank 103 through the electrolyte circulation pipeline. The pump and valve assembly is installed on the electrolyte circulation pipeline and is used to drive the electrolyte to circulate within the pipeline. The polarization decoupling module, connected in parallel with the electrolyte circulation pipeline of the main operating module, includes three test cells: a positive electrode-side symmetrical cell 201, a negative electrode-side symmetrical cell 202, and a positive and negative electrode polarization acquisition cell 203. Both chambers of the positive electrode-side symmetrical cell 201 are connected to the electrolyte circulation pipeline corresponding to the positive electrode liquid tank 102, and both chambers of the negative electrode-side symmetrical cell 202 are connected to the electrolyte circulation pipeline corresponding to the negative electrode liquid tank 103. The positive electrode chamber of the positive and negative electrode polarization acquisition cell 203 is connected to the electrolyte circulation pipeline corresponding to the positive electrode liquid tank 102, and the negative electrode chamber is connected to the electrolyte circulation pipeline corresponding to the negative electrode liquid tank 103, for synchronously outputting the electrochemical signals of the three test cells. The test module 30 includes a charge-discharge instrument and an electrochemical workstation. The charge-discharge instrument is electrically connected to the charge-discharge battery 101 and three test batteries, respectively, and is used to control the charge-discharge of the charge-discharge battery 101, output constant current charging excitation to the three test batteries, and acquire their steady-state voltage. The electrochemical workstation is electrically connected to the three test batteries, respectively, and is used to acquire the electrochemical impedance spectroscopy data of each battery and the constant current charging transient response voltage curve with millisecond time resolution. The control module is connected to the main operation module, polarization decoupling module and test module 30 respectively. It is used to coordinate the control of electrolyte circulation and test timing, receive all data collected by test module 30 and transmit it to data analysis module. The data analysis module, communicating with the control module, is used to decouple the total polarization, ohmic polarization, activation polarization, and concentration polarization of the four half-cell reactions based on the received steady-state voltage and electrochemical impedance spectroscopy data; it is used to perform relaxation time distribution analysis on the electrochemical impedance spectroscopy data to obtain the characteristic relaxation time constant; and it is used to calculate the polarization component values ​​for cross-validation and evaluate the accuracy of the decoupling results by combining the transient response voltage curve and the characteristic relaxation time constant. The four half-cell reactions are the oxidation of ferrous iron at the positive electrode, the reduction of ferric iron at the positive electrode, the oxidation of chromium divalent at the negative electrode, and the reduction of chromium trivalent at the negative electrode.

[0037] In some embodiments, the positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202, and the positive and negative electrode polarization acquisition battery 203 adopt completely identical battery structures, and the electrode materials, proton exchange membranes, and flow channel structures are all kept the same.

[0038] In some embodiments, the electrochemical workstation employs a two-electrode testing mode to perform electrochemical impedance spectroscopy (EIS) tests on three test cells, with the tests conducted during the steady-state phase of constant-current charging of the corresponding cells.

[0039] In some embodiments, the control module switches the electrolyte flow path through a pump and valve matching device, so that the polarization decoupling module and the main operating module are in parallel synchronous operation or independent offline operation; the control module is also used to perform periodic intermittent tests on the three test batteries of the polarization decoupling module.

[0040] In some embodiments, the periodic intermittent test includes a test phase and a resting phase, with the test phase lasting 5 to 20 minutes and the resting phase lasting 1 to 30 minutes, to ensure that the electrolyte concentration gradient and electrode interface state return to a quasi-steady state before the next round of testing.

[0041] A cross-validated method for decoupling asymmetric polarization data of iron-chromium flow batteries, using any of the cross-validated methods described above, includes: S1. The control module drives the pump and valve device to synchronously circulate the positive electrolyte in the positive electrode chamber of the charge / discharge battery 101, the two chambers of the positive electrode side symmetrical battery 201, and the positive electrode chamber of the positive and negative electrode polarization acquisition battery 203. At the same time, the negative electrolyte is synchronously circulated in the negative electrode chamber of the charge / discharge battery 101, the two chambers of the negative electrode side symmetrical battery 202, and the negative electrode chamber of the positive and negative electrode polarization acquisition battery 203, forming a stable test condition. S2. Based on stable test conditions, the charge-discharge instrument is controlled by the control module to perform constant current charging on the three test batteries at the same current density as the charge-discharge battery 101, and the steady-state voltage of each battery before and after charging is collected. The total polarization of each battery is calculated through the steady-state voltage. The electrochemical workstation is controlled to perform electrochemical impedance spectroscopy test on the three test batteries and collect the electrochemical impedance spectroscopy data of each battery. S3. Based on the electrochemical impedance spectroscopy data, the ohmic resistance and charge transfer resistance of the three test cells are obtained by the data analysis module. Then, the total ohmic resistance and total charge transfer resistance of the positive and negative half-reactions of the positive electrode side symmetrical cell 201, negative electrode side symmetrical cell 202, and positive and negative electrode polarization acquisition cell 203 are obtained by disassembling them respectively. S4. Based on total polarization, ohmic resistance, charge transfer resistance, total ohmic resistance and total charge transfer resistance, the ohmic polarization, activation polarization and concentration polarization of the three test cells are calculated by the data analysis module. S5. Ohmic polarization, activation polarization, and concentration polarization based on the positive electrode side-symmetric cell 201, based on Fe 3+ / Fe 2+ The electrochemical reversibility of the redox couple was determined by setting the ohmic polarization and activation polarization of the reduction of ferric iron and the oxidation of ferrous iron in the positive electrode side symmetrical cell 201 to be equal, thus obtaining the polarization reference value of a single positive electrode half-reaction. S6. Based on the positive and negative electrode polarization, the ohmic polarization, activation polarization, concentration polarization, and positive electrode half-reaction polarization reference values ​​of battery 203 are collected, and the polarization value of the negative electrode trivalent chromium reduction reaction is calculated. S7. Based on the ohmic polarization, activation polarization, and concentration polarization of the negative electrode side-symmetric cell 202, as well as the polarization value of the negative electrode trivalent chromium reduction reaction, the polarization value of the negative electrode divalent chromium oxidation reaction is separated, and finally the ohmic polarization and activation polarization of the four half-cell reactions are decoupled.

[0042] In some embodiments, when the positive electrolyte in the positive electrode tank 102 is at 50% charge, in S5 the concentration polarization of the reduction of ferric iron and the oxidation of ferrous iron in the positive electrode side symmetrical cell 201 is further set to be equal, in S6 the concentration polarization of the reduction of ferric iron in the negative electrode is calculated simultaneously, and in S7 the concentration polarization of the oxidation of ferrous iron in the negative electrode is separated simultaneously, and finally the concentration polarization of the four half-cell reactions is decoupled to obtain the concentration polarization of the four half-cell reactions.

[0043] In some embodiments, a cross-validation step for the decoupling results is also included, as follows: Based on electrochemical impedance spectroscopy data, relaxation time distribution analysis was performed through the data analysis module to obtain the characteristic relaxation time constants corresponding to activation polarization and concentration polarization of the three test cells. During the static setting phase of the polarization decoupling module, the electrochemical workstation is controlled by the control module to acquire the constant current charging transient response voltage curves of the three test batteries with millisecond time resolution. Based on the characteristic relaxation time constant and transient response voltage curve, the voltage value at the corresponding moment is extracted, and the polarization component value for cross-validation is calculated. The cross-validation polarization component value is compared with the corresponding polarization value. If the deviation between the two is within the preset tolerance range, the decoupling result is confirmed to be valid; otherwise, a verification failure message is output.

[0044] In some embodiments, the transient response voltage curve used to calculate the polarization component values ​​for cross-validation is replaced with an open-circuit voltage relaxation curve with millisecond-level time resolution, acquired when the three test batteries stop constant current charging.

[0045] In some embodiments, in S2, when the voltage fluctuation amplitude is within a preset threshold and the duration is not less than 30 seconds, it is determined that a steady state has been reached and the corresponding voltage data is collected; the execution sequence of constant current charging test and electrochemical impedance spectroscopy test is as follows: after the constant current charging test reaches a steady state, the electrochemical impedance spectroscopy test is immediately executed to ensure that the two sets of test data correspond to highly consistent operating conditions.

[0046] In some embodiments, the preset threshold for the voltage fluctuation amplitude corresponding to the steady-state voltage acquisition in S2 is set to ±2mV~±5mV. When the fluctuation amplitude of the acquired battery voltage within the preset duration is within the above range, it is determined that a steady state has been reached and the corresponding voltage data is acquired.

[0047] In some embodiments, when the test condition is in the high SOC range (SOC ≥ 80%) or the low SOC range (SOC ≤ 20%), the preset threshold value of the voltage fluctuation amplitude is adjusted to ±5 mV to adapt to the small voltage fluctuation characteristics caused by the change of the electrolyte concentration gradient in the high and low SOC ranges, and to avoid the loss of effective data caused by overly strict steady-state determination conditions; when the test condition is in the medium SOC range (20% < SOC < 80%), the preset threshold value of the voltage fluctuation amplitude is adjusted to ±2 mV to improve the acquisition accuracy of the steady-state data in the medium SOC range and ensure the reliability of the basic data for polarization decoupling.

[0048] In some embodiments, the preset tolerance range of the deviation in the cross-validation step of the decoupling result is set to be no greater than 5%. When the relative deviation between the polarization component value for cross-validation and the corresponding decoupled polarization value is ≤ 5%, the decoupling result is confirmed to be valid.

[0049] In some embodiments, when the test scenario has high-precision characterization requirements such as screening of battery electrode material performance, quantitative evaluation of catalytic activity, and optimization of electrolyte formula, the preset tolerance range of the deviation is tightened to be no greater than 3% to ensure that the accuracy of the decoupled data meets the requirements of refined material performance comparison and optimization; when the test scenario has conventional inspection requirements such as online polarization monitoring and fault warning under long-term battery operating conditions, the preset tolerance range of the deviation can be relaxed to be no greater than 8% to adapt to the small data deviation caused by the operating condition fluctuation during online monitoring and ensure the stability of the verification process.

[0050] In some embodiments, for the discharge condition of the charge-discharge battery 101, the cross-validation asymmetric polarization data decoupling method for the iron-chromium flow battery further includes a polarization decoupling step under the discharge condition, which is specifically as follows: T1. Drive the pump-valve matching device through the control module to make the positive electrolyte circulate synchronously in the positive electrode chamber of the charge-discharge battery 101, the two chambers of the positive electrode side symmetric battery 201, and the positive electrode chamber of the positive and negative polarization acquisition battery 203, and at the same time make the negative electrolyte circulate synchronously in the negative electrode chamber of the charge-discharge battery 101, the two chambers of the negative electrode side symmetric battery 202, and the negative electrode chamber of the positive and negative polarization acquisition battery 203 to form a stable discharge test condition; T2. Based on the stable discharge test condition, control the charge-discharge instrument through the control module to perform constant current discharge on the three test batteries at the same discharge current density as the charge-discharge battery 101, collect the steady-state voltages of each battery before and after discharge, and calculate the total polarization of each battery under the discharge condition through the steady-state voltages; synchronously control the electrochemical workstation to perform electrochemical impedance spectroscopy tests on the three test batteries and collect the electrochemical impedance spectroscopy data of each battery under the discharge condition; T3. Based on the electrochemical impedance spectroscopy data under discharge conditions, the ohmic resistance and charge transfer resistance of the three test batteries are obtained by the data analysis module. Then, the total ohmic resistance and total charge transfer resistance of the positive and negative half-reactions of the positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202, and the positive and negative electrode polarization acquisition battery 203 under discharge conditions are obtained respectively. T4. Based on the total polarization, ohmic resistance, charge transfer resistance, total ohmic resistance and total charge transfer resistance under discharge conditions, the ohmic polarization, activation polarization and concentration polarization of the three test batteries under discharge conditions are calculated by the data analysis module. T5. Ohmic polarization, activation polarization, and concentration polarization of the positive electrode side-symmetric cell 201 under discharge conditions, based on Fe 3+ / Fe 2+ The electrochemical reversibility of the redox couple was determined by setting the ohmic polarization and activation polarization of the reduction of ferric iron and the oxidation of ferrous iron in the positive electrode side symmetrical cell 201 to be equal, thus obtaining the polarization reference value of a single positive electrode half-reaction. T6. Based on the positive and negative electrode polarization, the ohmic polarization, activation polarization, concentration polarization, and positive electrode half-reaction polarization reference values ​​of battery 203 under discharge conditions are collected, and the polarization value of the positive electrode trivalent iron reduction reaction under discharge conditions is calculated. T7. Based on the ohmic polarization, activation polarization, and concentration polarization of the negative electrode side-symmetric battery 202 under discharge conditions, as well as the polarization value of the positive electrode trivalent iron reduction reaction, the polarization value of the negative electrode divalent chromium oxidation reaction under discharge conditions is separated, and finally the ohmic polarization and activation polarization of the four half-cell reactions under discharge conditions are decoupled.

[0051] In some embodiments, when the state of charge of the positive electrolyte in the positive electrode tank 102 is 50%, in T5, the concentration polarization of the reduction of ferric iron and the oxidation of ferrous iron in the symmetrical battery 201 on the positive electrode side is further set to be equal. In T6, the concentration polarization of the reduction of ferric iron in the positive electrode under the discharge condition is calculated simultaneously. In T7, the concentration polarization of the oxidation of ferrous chromium in the negative electrode under the discharge condition is separated simultaneously. Finally, the concentration polarization of the four half-cell reactions under the discharge condition is obtained by decoupling.

[0052] In some embodiments, a discharge condition cross-validation step is also provided for the decoupling results under discharge conditions, as detailed below: Based on the electrochemical impedance spectroscopy data collected under discharge conditions, the relaxation time distribution analysis was performed through the data analysis module to obtain the characteristic relaxation time constants corresponding to activation polarization and concentration polarization of the three test cells under discharge conditions. During the static setting phase of the polarization decoupling module, the electrochemical workstation is controlled by the control module to acquire the millisecond-level time resolution constant current discharge transient response voltage curves of the three test batteries. Based on the characteristic relaxation time constant and transient response voltage curve corresponding to the discharge condition, the voltage value at the corresponding moment is extracted, and the polarization component value for cross-validation under the discharge condition is calculated. The polarization component value used for cross-validation under the discharge condition is compared with the polarization value of the corresponding discharge condition. If the deviation between the two is within the preset tolerance range, the decoupling result under the discharge condition is confirmed to be valid; otherwise, a verification failure message is output.

[0053] In some embodiments, the transient response voltage curve used to calculate the polarization component value for cross-validation under discharge conditions is replaced with the open-circuit voltage relaxation curve with millisecond time resolution, which is collected starting when the three test batteries stop constant current discharge.

[0054] The technical concept of this invention is as follows: This invention includes a supporting design for an asymmetric polarization data decoupling system and method for iron-chromium redox flow batteries, as well as a dedicated cross-validation mechanism. The core solution is as follows: 1. System Core Architecture: The decoupled system consists of five core units: the main operation module, the polarization decoupling module, the testing module 30, the control module, and the data analysis module. The main operation module is a standard iron-chromium redox flow battery system, providing an electrolyte environment consistent with actual operating conditions. The polarization decoupling module, the core of the invention, is connected in parallel with the main operation module and includes three types of test batteries: a positive electrode-side symmetrical battery 201, a negative electrode-side symmetrical battery 202, and a positive and negative electrode polarization acquisition battery 203, all with identical electrode, membrane, and flow channel structures. It can simultaneously acquire polarization data highly matched to the operating conditions of the main battery. The testing module 30 is equipped with a charge-discharge instrument and an electrochemical workstation, enabling high-precision acquisition of steady-state voltage, electrochemical impedance spectroscopy (EIS), and millisecond-level transient response voltage curves. The control module is responsible for the coordinated control of the entire system's liquid circuit, timing, and operating conditions. The data analysis module undertakes the core functions of polarization decoupling calculation, relaxation time distribution (DRT) analysis, and cross-validation calculation.

[0055] 2. Core method for decoupling asymmetric polarization: First, the positive and negative electrode electrolytes are circulated in three types of test cells according to a preset configuration. Steady-state voltage and EIS data of each cell are simultaneously collected under specific operating conditions. The total polarization, ohmic polarization, activation polarization, and concentration polarization of each cell are calculated. Then, based on the Fe of the positive electrode... 3+ / Fe 2+ The excellent electrochemical reversibility of the redox couple establishes a benchmark for the polarization symmetry of oxidation and reduction reactions in symmetrical cells. By constructing and solving a set of algebraic equations, the polarization components of the trivalent chromium reduction reaction and the divalent chromium oxidation reaction at the negative electrode are separated in sequence, ultimately achieving complete decoupling of the ohmic polarization and activation polarization components of the four half-cell reactions. Under the specific condition of a positive electrode electrolyte SOC of 50%, based on the assumption of concentration polarization symmetry of the positive electrode redox couple, the full component of concentration polarization can be precisely decoupled.

[0056] 3. Decoupling Result Cross-validation Mechanism: The EIS data is deconvolved through DRT analysis to identify the characteristic relaxation time constants corresponding to the activation polarization and concentration polarization response processes; combined with the constant current charging transient response voltage curve with millisecond-level time resolution, the voltage data at the corresponding time nodes is extracted, and the polarization component verification value is calculated; the verification value is compared with the polarization results obtained by the decoupling method, and the accuracy and reliability of the decoupling results are confirmed through deviation verification, realizing mutual verification between frequency domain analysis and time domain analysis.

[0057] A cross-validation asymmetric polarization data decoupling system for iron-chromium redox flow batteries includes a main operation module, a polarization decoupling module, a test module 30, a control module, and a data analysis module.

[0058] The main operating module is a standard iron-chromium redox flow battery system, including a charge-discharge battery 101 for energy conversion, a positive electrode liquid tank 102 and a negative electrode liquid tank 103 for storing positive and negative electrolytes respectively, and is equipped with auxiliary equipment such as pumps and valves to drive electrolyte circulation.

[0059] The polarization decoupling module is the core of this invention. It is connected in parallel with the electrolyte circulation pipeline of the main operating module, ensuring that the electrolyte flowing through it is completely synchronized with the state (temperature, SOC, SOH) of the main battery. This module is used for online synchronous measurement of the asymmetric polarization data of the positive and negative electrolytes. This module contains three key test cells: Positive electrode side-symmetric cell 201: Both of its chambers (typically the positive and negative electrode chambers) are supplied with positive electrode electrolyte from the positive electrode tank 102; the electrochemical response of this cell is only related to the Fe at the positive electrode. 3+ / Fe 2+ It is related to electricity.

[0060] A symmetrical battery 202 with a negative electrode side: both chambers are supplied with negative electrode electrolyte from the negative electrode tank 103; the electrochemical response of this battery is only related to the Cr of the negative electrode. 3+ / Cr 2+ It is related to electricity.

[0061] Positive and negative polarization acquisition battery 203: This is a standard "asymmetric" battery, in which positive electrolyte is introduced into the positive electrode chamber and negative electrolyte is introduced into the negative electrode chamber. Its structure and operation are similar to the main charge and discharge battery 101, but the aging degree of internal components such as electrodes is closer to that of symmetric batteries, and the size can be smaller, which is specifically used for precise electrochemical measurement.

[0062] The positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202, and the positive and negative electrode polarization acquisition battery 203 have the same battery structure, including electrode materials, the type and thickness of the proton exchange membrane, and the flow channel structure, thereby eliminating the systematic error introduced by the difference in battery structure and ensuring the comparability of measurement results.

[0063] Test module 30 provides high-precision electrochemical testing capabilities, including: The charge / discharge instrument is electrically connected to the positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202, and the positive and negative electrode polarization acquisition battery 203, and is used to perform normal charge / discharge tests on them or apply constant current charging to test steady-state voltage.

[0064] The electrochemical workstation is electrically connected to the positive electrode-side symmetrical battery 201, the negative electrode-side symmetrical battery 202, and the positive and negative electrode polarization acquisition battery 203. It has two core functions: first, to perform electrochemical impedance spectroscopy (EIS) testing to obtain kinetic parameters such as the battery's ohmic resistance and charge transfer resistance; and second, to provide high-precision voltage acquisition function to record the constant current charging transient response voltage curve with millisecond-level time resolution.

[0065] EIS testing can be performed in a simple two-electrode mode, increasing ease of operation.

[0066] The control module is the brain of the entire system. Through its connection with other modules, it coordinates and controls the operation of the charging and discharging battery 101 and the synchronous testing of the polarization decoupling module. It can control the pump valve to switch the liquid circuit, so that the polarization decoupling module can be connected in parallel with the main operating module (for synchronous online testing) or run independently (for calibration or offline research). At the same time, it can precisely control the timing of the test module 30 and perform periodic intermittent tests.

[0067] The data analysis module is a software system that communicates with the control module. It is responsible for receiving massive amounts of test data and executing complex algorithms. Its core functions include: a) Polarization decoupling calculation: Based on the steady-state voltage and EIS data of the positive electrode side symmetrical cell 201, the negative electrode side symmetrical cell 202, and the positive and negative electrode polarization acquisition cell 203, a set of algebraic equations is used to automatically calculate and separate the total polarization, ohmic polarization, activation polarization and / or concentration polarization of the four half-cell reactions involved in the charge and discharge test of the iron-chromium redox flow battery.

[0068] b) DRT analysis: Relaxation time distribution (DRT) analysis is performed on EIS data. DRT can deconvolve complex impedance spectra in the time domain to obtain a series of characteristic relaxation time constants, which correspond to the characteristic time scales of physicochemical processes (such as charge transfer and mass diffusion) in electrochemical systems.

[0069] c) Cross-validation calculation: Based on the constant current charging transient response voltage curve and characteristic relaxation time constant with millisecond time resolution, the polarization component values ​​used for cross-validation are calculated, and the accuracy and precision of the polarization decoupling results are further evaluated.

[0070] To address the aforementioned technical problems, this invention also provides a cross-validated method for decoupling asymmetric polarization data in iron-chromium redox flow batteries. This method employs the cross-validated iron-chromium redox flow battery asymmetric polarization data decoupling system described above and includes the following steps: Steps S1-S4: Data acquisition and preliminary processing.

[0071] S1. The positive and negative electrolytes are circulated in the positive electrode symmetrical battery 201, the negative electrode symmetrical battery 202, and the positive and negative electrode polarized acquisition battery 203 according to the preset configuration (symmetrical or asymmetrical).

[0072] S2. Under specific operating conditions (such as given current density, temperature, SOC, and SOH), the positive-side symmetrical battery 201, the negative-side symmetrical battery 202, and the positive and negative polarization acquisition battery 203 are subjected to constant current charging, and EIS testing is performed simultaneously after obtaining the steady-state voltage. The total polarization is calculated from the steady-state voltage, and the ohmic resistance and charge transfer resistance are obtained by analyzing the EIS spectrum (e.g., by equivalent circuit fitting).

[0073] S3. Based on the EIS data of the positive electrode side symmetrical battery 201, analyze the total ohmic resistance and total charge transfer resistance of the trivalent iron reduction and divalent iron oxidation reactions in the positive electrode liquid; based on the EIS data of the negative electrode side symmetrical battery 202, analyze the total ohmic resistance and total charge transfer resistance of the trivalent chromium reduction and divalent chromium oxidation reactions in the negative electrode liquid; based on the EIS data of the positive and negative electrode polarization acquisition battery 203, analyze the total ohmic resistance and total charge transfer resistance of the trivalent chromium reduction and divalent iron oxidation reactions in the negative electrode liquid and the positive electrode liquid.

[0074] S4. According to Ohm's law, ohmic polarization and activation polarization are obtained from ohmic resistance and charge transfer resistance, respectively. Finally, concentration polarization η_conc_decouple is obtained by subtracting ohmic polarization and activation polarization from total polarization, thereby obtaining three polarization values ​​of positive electrode side symmetrical cell 201, negative electrode side symmetrical cell 202 and positive and negative electrode polarization acquisition cell 203 under specific operating conditions.

[0075] Steps S5-S7: Asymmetric polar decoupling. This is the key to the method of this invention.

[0076] S5. Establish a baseline. Utilize Fe 3+ / Fe 2+The redox couple possesses excellent electrochemical reversibility and high reactivity. This invention proposes a key and reasonable assumption: in the positive electrode-side symmetrical cell 201, the ohmic polarization and activation polarization of the ferrous oxidation reaction and the ferric reduction reaction occurring during charging are approximately equal. Therefore, half of the ohmic polarization and activation polarization values ​​measured from the positive electrode-side symmetrical cell 201 represent the corresponding polarization contribution of a single ferrous oxidation or ferric reduction reaction.

[0077] S6. Separate the negative electrode reduction reaction. The polarization values ​​of the positive and negative electrode polarization collection battery 203 are the sum of the polarization values ​​of the positive electrode ferrous oxidation and the negative electrode trivalent chromium reduction. Since the polarization value of ferrous oxidation has been determined in step S5, the polarization values ​​of the negative electrode trivalent chromium reduction reaction can be accurately separated by simple subtraction.

[0078] S7. Separate the negative electrode oxidation reaction. The polarization values ​​of the symmetrical cell 202 on the negative electrode side are the sum of the polarization values ​​of the trivalent chromium reduction and divalent chromium oxidation reactions. Since the polarization value of the trivalent chromium reduction reaction has been determined in step S6, another unknown quantity—the polarization values ​​of the divalent chromium oxidation reaction on the negative electrode—can be separated by subtraction.

[0079] Thus, this invention successfully decouples the ohmic polarization and activation polarization contributions of the four key half-cell reactions involved in the charging and discharging process of an iron-chromium redox flow battery. Decoupling of the discharge process can be achieved through similar logic.

[0080] Under specific conditions, such as when the SOC of the electrolyte in the positive electrode tank 102 is 50%, it can be further assumed that the concentration polarization of the two reactions in the positive electrode side symmetrical cell 201 is also equal, thereby precisely decoupling the concentration polarization to each half-cell reaction.

[0081] To address the aforementioned technical problems, this invention also proposes a cross-validation method based on DRT analysis and transient response voltage curves with millisecond-level time resolution (i.e., a cross-validation mechanism, implemented based on a cross-validation-based decoupling method for asymmetric polarization data in iron-chromium flow batteries), to ensure the reliability of the decoupling results, comprising the following steps: Steps V1-V2: Obtain the relaxation time constant and high-resolution transient voltage curves for each polarization characteristic.

[0082] V1. The data analysis module processes EIS data and, through DRT analysis, identifies and obtains the characteristic relaxation time constants τ_act, τ_act_end, τ_conc, and τ_conc_end corresponding to the activation polarization and concentration polarization response processes of the positive electrode-side symmetrical battery 201, the negative electrode-side symmetrical battery 202, and the positive and negative electrode polarization acquisition battery 203. Among them, τ_act is the characteristic relaxation time constant corresponding to the peak value of the activation polarization response, τ_act_end is the time constant corresponding to the decay of the spectral peak corresponding to the activation polarization to the tail, τ_conc is the time constant corresponding to the peak value of the concentration polarization response, and τ_conc_end is the time constant corresponding to the decay of the spectral peak corresponding to the concentration polarization to the tail. V2. When the polarization decoupling module is in the static stage, the electrochemical workstation performs a high-precision voltage acquisition function to record the millisecond-level time resolution constant current charging transient response voltage curves of the positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202 and the positive and negative electrode polarization acquisition battery 203. The sampling interval is 1 millisecond, and the recording time covers the entire concentration polarization response process. V3-V4: Polarization calculation based on high-resolution transient voltage curves.

[0083] V3, the data analysis module analyzes the constant current charging transient response voltage curve with millisecond-level time resolution for each battery: a) Extract the steady-state open-circuit voltage value V_ocv before charging; b) Based on the activation polarization characteristic relaxation time constant τ_act_end, determine the time point t=τ_act_end on the voltage curve in step V2, and extract the voltage value V_τ_act_end corresponding to that moment; c) Based on the relaxation time constant τ_conc_end of the concentration polarization characteristics, determine the time point t=τ_conc_end on the voltage curve in step V2, and extract the voltage value V_τ_conc_end corresponding to that moment; V4. For each cell, calculate and verify the polarization value: a) Calculate the verification value of the total polarization: η_total_verify = V_τ_conc_end - V_ocv; b) Calculate the verification value of the sum of ohmic polarization and activation polarization: η_ohm + act_verify = V_τ_act_end - V_ocv; c) Calculate the verification value of concentration polarization: η_conc_verify = V_τ_conc_end - V_τ_act_end; V5-V6: Comparison and Confirmation.

[0084] V5. Compare the concentration polarization verification value η_conc_verify of each battery calculated in step V4 with the concentration polarization value η_conc_decouple of the corresponding battery calculated by the polarization decoupling method in step S4 of claim 6. V6. If the deviations of η_conc_verify and η_conc_decouple for each battery are both within the preset tolerance range, the verification is successful, confirming that the polarization decoupling result has high accuracy; otherwise, a verification failure flag is output, indicating that the test conditions or model assumptions need to be checked.

[0085] Furthermore, the voltage curve used to verify the concentration polarization value can also be the open-circuit voltage relaxation curve with millisecond-level time resolution, recorded by the positive electrode-side symmetrical cell 201, the negative electrode-side symmetrical cell 202, and the positive and negative electrode polarization acquisition cell 203 when charging stops.

[0086] The system, decoupling method, and cross-validation method of this invention are also applicable to other flow battery systems besides iron-chromium flow batteries, including but not limited to vanadium redox flow batteries, zinc-based flow batteries, iron-based flow batteries, organic flow batteries, sodium polysulfide / bromine flow batteries, and hydrogen-bromine flow batteries, for online decoupling and cross-validation of the asymmetric polarization data of their positive and negative electrodes.

[0087] Example 1: Figure 1 This is a schematic diagram of the hardware connection of the iron-chromium redox flow battery asymmetric polarization data decoupling system for cross-validation of this invention. Figure 1 As shown, the hardware of the polarization data decoupling system in this embodiment includes a charge / discharge battery 101, a positive electrode liquid tank 102, a negative electrode liquid tank 103, a positive electrode side symmetrical battery 201, a negative electrode side symmetrical battery 202, a positive and negative electrode polarization acquisition battery 203, a test module 30, and supporting devices such as pumps and valves for driving electrolyte circulation.

[0088] In this embodiment, the charge / discharge battery 101 is a stack composed of four individual cells connected in series, and its single electrode has a geometric area of ​​3000 cm². 2 The electrode material of the fuel cell stack is thermally activated carbon cloth, and the proton exchange membrane is made of Nafion material. 212. The flow channel plate is made of graphite and designed with interdigitated flow channels. The positive electrode liquid tank 102 and the negative electrode liquid tank 103 both have a volume of 200L. The initial composition of the positive and negative electrode electrolytes is the same, both containing 1.0M FeCl2, 1.3M CrCl3 and 2.0M HCl.

[0089] The positive electrode-side symmetrical battery 201, the negative electrode-side symmetrical battery 202, and the positive and negative electrode polarization acquisition battery 203 are all single cells, with a single electrode geometric area of ​​1200 cm². 2To eliminate systematic errors caused by structural differences, the positive electrode-side symmetrical battery 201, the negative electrode-side symmetrical battery 202, and the positive and negative electrode polarization acquisition battery 203 all employ identical battery structures. Furthermore, the electrode materials, proton exchange membranes, and flow channel plates used in these batteries are identical in type, specifications, and processing technology to those used in the main charge / discharge battery 101. During system operation, the electrolyte flow rate of each battery is controlled at 1.0 mL / (min·cm). 2 The electrolyte temperature is maintained at 60℃.

[0090] The positive and negative chambers of the positive electrode-side symmetrical battery 201 have their inlets and outlets connected to the positive electrode liquid tank 102 via valves; in this configuration, only Fe occurs on both sides of the battery interior. 3+ / Fe 2+ The redox reaction of the redox couple results in the same theoretical thermodynamic equilibrium potential, and the theoretical open-circuit voltage is zero. The voltage response observed in actual tests originates entirely from various polarizations generated during battery operation. The positive and negative chambers of the symmetrical negative electrode battery 202 have their inlets and outlets connected to the negative electrode liquid tank 103 via valves. Under this configuration, only Cr polarization occurs on both sides of the battery interior. 3+ / Cr 2+ The theoretical open-circuit voltage of the redox reaction is also zero, and the measured voltage is entirely derived from polarization. The positive and negative polarization acquisition cell of battery 203 has its inlet and outlet connected to the positive liquid tank 102; the inlet and outlet of its negative cell are connected to the negative liquid tank 103; this is a standard asymmetric configuration that simulates the single-cell behavior of charge-discharge battery 101.

[0091] The test module 30 includes a charge-discharge instrument and an electrochemical workstation. The charge-discharge instrument is a multi-channel battery testing system, with each channel individually connected to a battery (positive electrode side symmetrical battery 201, negative electrode side symmetrical battery 202, and positive and negative electrode polarization acquisition battery 203) to ensure that the tests do not interfere with each other.

[0092] The electrochemical workstation consists of three single-channel electrochemical workstations with an EIS measurement frequency range of 100kHz to 0.1Hz, covering the entire process from inductance and charge transfer to diffusion. The data sampling interval of its voltage acquisition module can be as low as 1μs, which fully meets the recording requirements of constant current charging transient response voltage curves with millisecond-level time resolution. The three electrochemical workstations are respectively connected to the positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202, and the positive and negative electrode polarization acquisition battery 203, and are configured in a two-electrode test mode to simplify wiring and reduce instability introduced by the reference electrode.

[0093] The control module adopts a distributed control system architecture based on a programmable logic controller (PLC) and a host computer (PC). A dedicated control program runs on the host computer, precisely controlling the speed of all circulating pumps and the on / off status of each valve via the PLC. Following a preset test sequence, it sends precise commands, including current magnitude, test duration, and EIS test parameters, to the test module 30. Simultaneously, the control module receives raw voltage, current, and impedance data collected from the test module 30 in real time. Communication between the control module and each actuator and test equipment employs a highly reliable industrial communication protocol, ensuring the real-time nature and reliability of command issuance and data upload.

[0094] The data analysis module is dedicated data analysis software running on the host computer. This software receives raw test data from the control module and integrates and executes a series of core algorithms, including data processing, polarization decoupling calculation, relaxation time distribution analysis, and cross-validation. Polarization decoupling calculation is based on solving a system of established algebraic equations; relaxation time distribution analysis employs regularization methods (such as Tikhonov regularization) and features automatic characteristic peak identification; the cross-validation algorithm compares the polarization results obtained by different methods. All analysis results are displayed in real-time through a graphical user interface and stored in the system's structured database, forming a complete test and analysis record.

[0095] Example 2: Figure 2 This is a flowchart of the asymmetric polarization data decoupling method for iron-chromium redox flow batteries according to the present invention; Figure 3 It is the electrochemical impedance spectrum (Nyquist plot) of the positive and negative polarization acquisition battery 203 under specific operating conditions and the fitting results of its equivalent circuit; Figure 4 The polarization decoupling results of the positive and negative polarization acquisition battery 203 under different SOCs; Figure 5 This is the relationship between the ohmic polarization and activation polarization of the half-cell where the three typical electrochemical reactions occur during the charging of rechargeable battery 101 and the state of charge (SOC).

[0096] Combination Figures 2 to 5 This embodiment details how to decouple the polarization components of the four half-cell reactions from the total polarization and EIS data of symmetric and asymmetric cells by establishing and solving a system of algebraic equations.

[0097] The total voltage V_cell of a battery can be expressed as the sum of the equilibrium potential E_eq and various overpotentials (i.e., polarization η). For the charge and discharge process, the total polarization η_total can be decomposed into ohmic polarization η_ohm, activation polarization η_act, and concentration polarization η_conc, i.e.: V_cell=E_eq+n_total=E_eq+n_ohm+n_act+n_conc; Ohmic polarization follows Ohm's law, η_ohm = I × R_ohm, where R_ohm is the ohmic resistance; activation polarization follows the Butler-Volmer equation, which can be approximated as η_act = I × R_ct under small overpotentials or specific simplifications, where R_ct is the charge transfer resistance; concentration polarization is related to the mass transfer process. This decomposition is the basis of electrochemical impedance spectroscopy analysis, and these processes can be distinguished by the responses at different frequencies.

[0098] The decoupling method in this embodiment establishes a system of equations based on the following measurements and assumptions: For the positive electrode-side symmetrical battery 201, during charging, ferrous iron oxidation (ox) occurs on one side, while ferric iron reduction (red) occurs on the other side. Based on Fe... 3+ / Fe 2+ The high reversibility of the redox couple is assumed to be based on the symmetry of the ohmic and activation polarizations of its oxidation and reduction reactions, i.e.: η_Fe_ox_ohm≈η_Fe_red_ohm, and η_Fe_ox_act≈η_Fe_red_act; The measured total polarization is: η_Sym_Pos = η_Fe_ox + η_Fe_red; Therefore, the polarization component of a single positive electrode half-cell reaction can be expressed as: η_Fe_ox_ohm=η_Fe_red_ohm=0.5*η_Sym_Pos_ohm; η_Fe_ox_act=η_Fe_red_act=0.5*η_Sym_Pos_act; In this embodiment, as Figure 3 As shown, the ohmic resistance and charge transfer resistance are obtained based on the equivalent circuit fitting. This result can also be verified or estimated by the high-frequency intercept and semicircle diameter of the EIS spectrum, respectively.

[0099] For the symmetrical battery 202 on the negative electrode side, during charging, divalent chromium oxidation occurs on one side, while trivalent chromium reduction occurs on the other side. Given that Cr... 3+ / Cr 2+ The dynamic properties of the redox couple are assumed to be symmetrical only in terms of ohmic polarization, while the activation polarization is asymmetrical.

[0100] The measured total polarization is: η_Sym_Neg = η_Cr_ox + η_Cr_red; Among them, η_Sym_Neg_ohm=η_Cr_ox_ohm+η_Cr_red_ohm, η_Sym_Neg,act=η_Cr_ox_act+η_Cr_red_act.

[0101] For the positive and negative polarized acquisition battery 203, during the charging process, ferrous iron is oxidized at the positive electrode and chromium is reduced at the negative electrode.

[0102] The measured total polarization is: η_Asym = η_Fe_ox + η_Cr_red; Among them, η_Asym_ohm=η_Fe_ox_ohm+η_Cr_red_ohm, η_Asym_act=η_Fe_ox_act+η_Cr_red_act.

[0103] Based on the above measurements and assumptions, a system of equations can be established and the unknown polarization components can be solved: Known quantities: η_Sym_Pos, η_Sym_Neg, η_Asym and their ohmic and activation components obtained through EIS.

[0104] Based on the symmetry assumption of the positive electrode side-symmetric cell 201, the components of η_Fe_ox can be obtained.

[0105] Substituting the relationship between the positive and negative polarization acquisition cell 203, the components of η_Cr_red can be obtained: η_Cr_red_ohm=η_Asym_ohm-η_Fe_ox_ohm; η_Cr_red_act=η_Asym_act-η_Fe_ox_act; Finally, using the summation relationship of the symmetrical battery 202 on the negative electrode side, the components of η_Cr_ox are obtained: η_Cr_ox_ohm=η_Sym_Neg_ohm-η_Cr_red_ohm; η_Cr_ox_act=η_Sym_Neg_act-η_Cr_red_act; At this point, the ohmic polarization and activation polarization of each half-cell reaction are completely decoupled.

[0106] Concentration polarization is calculated using the formula η_conc=η_total-η_ohm-η_act.

[0107] It is worth noting that when the electrolyte SOC in the positive electrode tank 102 is 50%, it can be further assumed that the concentration polarization in the symmetrical cell 201 on the positive electrode side is also symmetrical, thus similarly decoupling the concentration polarization. This is because at 50% SOC, the concentration gradients of reactants and products are relatively balanced, and the mass transfer resistance is similar in both the forward and reverse reactions. However, under extreme SOC conditions, the polarization effect is more significant, and the symmetry assumption fails.

[0108] According to the polarization decoupling process described in this embodiment, polarization decoupling is performed near five typical SOC points (0%, 25%, 50%, 75%, and 100%) during the charging process of battery 101. Some results are as follows: Figure 4 and Figure 5 As shown.

[0109] Figure 4 This is a decoupling of the overall polarization of the positive and negative polarization acquisition battery 203.

[0110] 1. Ohmic polarization: As the SOC increases from 0% to 75%, the ohmic polarization increases significantly from about 115mV to about 150mV, and decreases slightly to about 141mV at 100% SOC; this indicates that the ohmic resistance is greatest in the medium to high SOC range, which may be related to the resistance to electrolyte ion migration and / or the change in conductivity caused by hydrogen ion migration.

[0111] 2. Activation polarization: The contribution of activation polarization is minimal across the entire SOC range, consistently below 5mV; this indicates that the electrochemical reaction kinetics are relatively smooth and the reaction resistance is small in this battery system.

[0112] 3. Concentration polarization: It is relatively high at low SOC (0%) (about 32 mV), then decreases to about 22 mV at 25% SOC, and remains stable at 50% and 75% SOC (about 20-22 mV), and finally rises sharply to about 48 mV at 100% SOC; indicating that the increased concentration gradient at high SOC leads to a significant increase in mass transfer resistance.

[0113] Figure 5 This is a polar decoupling of specific electrochemical reactions.

[0114] 1. Ohmic polarization: The oxidation reaction of ferrous iron gradually increases with the increase of SOC, reaching a peak value (about 72mV) at 75% SOC and then decreasing slightly. The reduction reaction of trivalent chromium gradually increases with the increase of SOC, and then decreases slightly after reaching a peak at 75% SOC. The oxidation reaction of divalent chromium: does not change much throughout the entire SOC range, and always fluctuates around 60mV.

[0115] 2. Activation polarization: Oxidation reaction of ferrous iron: always extremely low, close to 0mV; The reduction reaction of trivalent chromium remains at a low level, between 5 and 10 mV, and is lowest at 50% SOC; The oxidation reaction of divalent chromium is highest at low SOC (0%) (approximately 32 mV), then drops sharply to near 0 mV at 25% and 50% SOC, and rises again in subsequent SOC ranges.

[0116] Figure 4 and Figure 5 Together, they revealed the evolution of battery polarization characteristics with SOC: 1. Ohmic polarization is the main source of voltage loss in iron-chromium flow batteries, and it reaches its peak near 75% SOC. Optimizing the battery's internal resistance is the key to improving voltage efficiency.

[0117] 2. Concentration polarization increases sharply at high SOC (100%), becoming a loss term that cannot be ignored, suggesting that the electrolyte concentration distribution under high charge state needs to be managed.

[0118] 3. The overall contribution of activation polarization is small, but the activation polarization of the divalent chromium oxidation reaction is higher at low SOC, indicating that its reaction kinetics are significantly affected by SOC.

[0119] In summary, this decoupling method clearly quantifies the contribution of each polarization component, providing key data support for targeted optimization of the performance of iron-chromium flow batteries.

[0120] Example 3: To ensure the reliability of the decoupling results in Example 2, this invention proposes an innovative cross-validation method: combining frequency domain EIS / DRT analysis with time domain millisecond-level constant current charging transient voltage response to mutually verify the decoupling results, thereby significantly improving the credibility of the data.

[0121] Figure 6 This is a flowchart of the cross-validation method of the present invention. Figure 7 for Figure 3 A schematic diagram of the DRT analysis results of the Nyquist plot. Figure 8 The transient response voltage curve of constant current charging of the symmetrical battery 201 on the positive electrode side with millisecond time resolution is shown when the SOC of the positive electrode electrolyte is 100%. The sampling interval is 1 millisecond, and the recording time covers the entire concentration polarization response process, which is used to illustrate the definition of each voltage characteristic point in the cross-validation method.

[0122] Combination Figure 6 , Figure 7 and Figure 8 This embodiment details how to achieve cross-validation based on DRT analysis and transient response voltage curves. The specific steps are as follows: Step V1: Perform DRT analysis on the EIS data to obtain the characteristic relaxation time constant.

[0123] The core of DRT analysis is to convert the frequency domain impedance data Z(ω) into the time domain relaxation time distribution function γ(τ), which involves solving an ill-conditioned Fredholm integral equation inverse problem. This embodiment employs the Tikhonov regularization method and automatically selects the optimal regularization parameter λ using the L-curve criterion to achieve a balance between solution smoothness and goodness of fit. The analysis is performed on a host computer using a Python-based software package, enabling DRT calculation, automatic peak identification, and statistical analysis within seconds.

[0124] like Figure 7 As shown, for Figure 3 After performing DRT analysis on the Nyquist curve and obtaining the spectrum (γ(τ)-τ), by selecting intervals of the original data in the Nyquist curve and performing DRT fitting respectively, it is easy to obtain the correspondence between each DRT peak and each region in the Nyquist curve, and thus determine each relaxation process: The first peak (mid-frequency region) corresponds to the charge transfer process (activation polarization), which is the first (R,CPE) element in the equivalent circuit; the characteristic relaxation time constant τ_act at the peak is about 0.65 milliseconds, and the time constant τ_act_end corresponding to the decay of the spectral peak to the tail is about 1.4 milliseconds.

[0125] The second peak (high frequency region) reflects the inductive effect in the test environment, corresponding to component L, and is unrelated to the battery electrochemical reaction.

[0126] The third peak (mid-to-low frequency region): corresponds to partial concentration polarization, characterizing the diffusion effect of porous electrodes, reflecting the coupling of ion transport resistance and distributed capacitance in the pore network, which is the second (R,CPE) element in the equivalent circuit.

[0127] The fourth peak (low-frequency region) corresponds to another part of concentration polarization, describing the semi-infinite diffusion process outside the macroscopic surface of the electrode, corresponding to the Wo element in the equivalent circuit. The characteristic relaxation time constant τ_conc at the peak is approximately 6.55 seconds, and the time constant τ_conc_end corresponding to the decay of its spectral peak to the tail is approximately 18.5 seconds.

[0128] Step V2: Record the millisecond-level transient response voltage curve.

[0129] When the polarization decoupling module is in the static stage, the electrochemical workstation performs high-precision voltage acquisition, and records the constant current charging transient response voltage curves of the positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202, and the positive and negative electrode polarization acquisition battery 203 at a sampling interval of 1 millisecond, with a recording duration of 30 seconds.

[0130] Step V3: Extract characteristic voltage values ​​from the transient curve.

[0131] Taking the curve of the positive electrode side-symmetric battery 201 under the condition that the SOC of the positive electrode electrolyte is 100% as an example ( Figure 8 ): ①The steady-state open-circuit voltage V_ocv before charging is 0.0000V; ②Based on the characteristic relaxation time constant τ_act_end of activation polarization, V_τ_act_end can be obtained as 0.1314V; ③Based on the relaxation time constant τ_conc_end of concentration polarization characteristics, V_τ_conc_end can be obtained as 0.1800V.

[0132] Step V4: Calculate the verification values ​​for each polarization based on the transient curve.

[0133] From the above characteristic voltage, we can further calculate: ① The total polarization verification value η_total_verify is 0.1800V; ② The verification value of the sum of ohmic polarization and activation polarization, η_ohm+act_verify, is 0.1314V; ③ The concentration polarization verification value η_conc_verify is 0.0486V.

[0134] Step V5: Obtain the polarization value based on the EIS decoupling method.

[0135] Under the same test conditions (positive electrolyte SOC of 100%), the following results were obtained using a polarization decoupling method based on total polarization and EIS: ① For a half-cell in which the oxidation of ferrous iron occurs: Ohmic polarization is approximately 0.0715 V, and activation polarization is approximately 0.0003 V; ② For the positive electrode side symmetrical cell 201: the total polarization of the two reactions of oxidation of ferrous iron and reduction of ferric iron is 0.1909V, and the sum of concentration polarization η_conc_decouple is 0.0473V.

[0136] Step V6: Result Comparison and Verification.

[0137] Comparison of concentration polarization values ​​obtained by the two independent methods: ① Numerically, η_conc_verify (0.0486V) and η_conc_decouple (0.0473V) differ by only about 2.7%; ② Their respective proportions in the total polarization are 27.0% and 24.8%, with a difference of only about 2.2%.

[0138] The two results are highly consistent, which fully verifies the reliability of the polarization decoupling method in Example 2.

Claims

1. A cross-validated asymmetric polarization data decoupling system for iron-chromium redox flow batteries, characterized in that, include: The main operating module includes a rechargeable battery, a positive electrode liquid tank, a negative electrode liquid tank, an electrolyte circulation pipeline, and a pump and valve assembly. The positive electrode chamber of the rechargeable battery is connected to the positive electrode liquid tank, and the negative electrode chamber of the rechargeable battery is connected to the negative electrode liquid tank, all through the electrolyte circulation pipeline. The pump and valve assembly is installed on the electrolyte circulation pipeline and is used to drive the electrolyte to circulate within the pipeline. The polarization decoupling module, connected in parallel with the electrolyte circulation pipeline of the main operating module, includes three test cells: a positive electrode-side symmetrical cell, a negative electrode-side symmetrical cell, and a positive and negative electrode polarization acquisition cell. Both chambers of the positive electrode-side symmetrical cell are connected to the electrolyte circulation pipeline corresponding to the positive electrode tank, and both chambers of the negative electrode-side symmetrical cell are connected to the electrolyte circulation pipeline corresponding to the negative electrode tank. The positive electrode chamber of the positive and negative electrode polarization acquisition cell is connected to the electrolyte circulation pipeline corresponding to the positive electrode tank, and the negative electrode chamber is connected to the electrolyte circulation pipeline corresponding to the negative electrode tank, for synchronously outputting electrochemical signals from the three test cells. The testing module includes a charge / discharge instrument and an electrochemical workstation. The charge / discharge instrument is electrically connected to the charge / discharge battery and three test batteries, respectively, and is used to control the charge / discharge of the charge / discharge battery, output constant current charging excitation to the three test batteries, and acquire their steady-state voltage. The electrochemical workstation is electrically connected to the three test batteries, respectively, and is used to acquire the electrochemical impedance spectroscopy data and the constant current charging transient response voltage curve with millisecond time resolution for each battery. The control module is connected to the main operation module, polarization decoupling module and test module respectively. It is used to coordinate the control of electrolyte circulation and test timing, receive all data collected by the test module and transmit it to the data analysis module. The data analysis module, communicating with the control module, is used to decouple the total polarization, ohmic polarization, activation polarization, and concentration polarization of the four half-cell reactions based on the received steady-state voltage and electrochemical impedance spectroscopy data; it is used to perform relaxation time distribution analysis on the electrochemical impedance spectroscopy data to obtain the characteristic relaxation time constant; and it is used to calculate the polarization component values ​​for cross-validation and evaluate the accuracy of the decoupling results by combining the transient response voltage curve and the characteristic relaxation time constant; the four half-cell reactions are the positive electrode oxidation reaction of ferrous iron, the positive electrode reduction reaction of ferric iron, the negative electrode oxidation reaction of ferrous chromium, and the negative electrode reduction reaction of ferric chromium.

2. The cross-validated asymmetric polarization data decoupling system for iron-chromium redox flow batteries according to claim 1, characterized in that, The positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the positive and negative electrode polarized acquisition battery adopt the same battery structure, and the electrode materials, proton exchange membranes, and flow channel structures are all the same.

3. The cross-validated asymmetric polarization data decoupling system for iron-chromium redox flow batteries according to claim 1, characterized in that, The electrochemical workstation uses a two-electrode testing mode to perform electrochemical impedance spectroscopy tests on three test cells. The tests are conducted during the steady-state phase of constant current charging of the corresponding cells.

4. The cross-validated asymmetric polarization data decoupling system for iron-chromium redox flow batteries according to claim 1, characterized in that, The control module switches the electrolyte flow path through a pump and valve matching device, so that the polarization decoupling module and the main operating module are in parallel synchronous operation or independent offline operation; the control module is also used to perform periodic intermittent tests on the three test batteries of the polarization decoupling module.

5. The cross-validated asymmetric polarization data decoupling system for iron-chromium redox flow batteries according to claim 4, characterized in that, The periodic intermittent test includes a testing phase and a settling phase. The testing phase lasts for 5 to 20 minutes, and the settling phase lasts for 1 to 30 minutes, to ensure that the electrolyte concentration gradient and electrode interface state return to a quasi-steady state before the next round of testing.

6. A method for decoupling asymmetric polarization data of iron-chromium redox flow batteries through cross-validation, characterized in that, The iron-chromium redox flow battery asymmetric polarization data decoupling system using any one of claims 1 to 5, wherein the cross-validated iron-chromium redox flow battery asymmetric polarization data decoupling method includes: S1. The control module drives the pump and valve device to synchronously circulate the positive electrolyte in the positive electrode chamber of the charge / discharge battery, the two chambers of the positive electrode side symmetrical battery, and the positive electrode chamber of the positive and negative polarization acquisition battery. At the same time, the negative electrolyte is synchronously circulated in the negative electrode chamber of the charge / discharge battery, the two chambers of the negative electrode side symmetrical battery, and the negative electrode chamber of the positive and negative polarization acquisition battery, forming a stable test condition. S2. Based on stable test conditions, the charge-discharge instrument is controlled by the control module to perform constant current charging on the three test batteries at the same current density as the charging and discharging batteries, and the steady-state voltage of each battery before and after charging is collected. The total polarization of each battery is calculated through the steady-state voltage. Simultaneously, the electrochemical workstation is controlled to perform electrochemical impedance spectroscopy tests on the three test batteries and collect the electrochemical impedance spectroscopy data of each battery. S3. Based on the electrochemical impedance spectroscopy data, the ohmic resistance and charge transfer resistance of each of the three test batteries are obtained by the data analysis module. Then, the total ohmic resistance and total charge transfer resistance of the positive and negative half-reactions of the positive electrode symmetrical battery, the negative electrode symmetrical battery, and the positive and negative electrode polarization acquisition battery are obtained by disassembling them respectively. S4. Based on total polarization, ohmic resistance, charge transfer resistance, total ohmic resistance and total charge transfer resistance, the ohmic polarization, activation polarization and concentration polarization of the three test cells are calculated by the data analysis module. S5. Ohmic polarization, activation polarization, and concentration polarization based on positive electrode side-symmetric cells, based on Fe 3+ / Fe 2+ The electrochemical reversibility of the redox couple was determined by setting the ohmic polarization and activation polarization of the reduction of ferric iron and the oxidation of ferrous iron in the symmetrical cell on the positive electrode side to be equal, thus obtaining the polarization reference value of a single positive electrode half-reaction. S6. Based on the positive and negative electrode polarization, the ohmic polarization, activation polarization, concentration polarization of the battery and the positive electrode half-reaction polarization reference value, the polarization value of the negative electrode trivalent chromium reduction reaction is calculated. S7. Based on the ohmic polarization, activation polarization, and concentration polarization of the negative electrode side-symmetric cell, as well as the polarization value of the negative electrode trivalent chromium reduction reaction, the polarization value of the negative electrode divalent chromium oxidation reaction is separated, and finally the ohmic polarization and activation polarization of the four half-cell reactions are decoupled.

7. The method for decoupling asymmetric polarization data of iron-chromium redox flow batteries through cross-validation according to claim 6, characterized in that, When the positive electrolyte in the positive electrode tank is 50% charged, in S5, the concentration polarization of the reduction of ferric iron and the oxidation of ferrous iron in the symmetrical cell on the positive electrode side is further set to be equal. In S6, the concentration polarization of the reduction of ferric iron in the negative electrode is calculated simultaneously. In S7, the concentration polarization of the oxidation of ferrous iron in the negative electrode is separated simultaneously. Finally, the concentration polarization of the four half-cell reactions is decoupled and obtained.

8. The method for decoupling asymmetric polarization data of iron-chromium redox flow batteries through cross-validation according to claim 6, characterized in that, It also includes a cross-validation step for the decoupling results, as detailed below: Based on electrochemical impedance spectroscopy data, relaxation time distribution analysis was performed through the data analysis module to obtain the characteristic relaxation time constants corresponding to activation polarization and concentration polarization of the three test cells. During the static setting phase of the polarization decoupling module, the electrochemical workstation is controlled by the control module to acquire the constant current charging transient response voltage curves of the three test batteries with millisecond time resolution. Based on the characteristic relaxation time constant and transient response voltage curve, the voltage value at the corresponding moment is extracted, and the polarization component value for cross-validation is calculated. The cross-validation polarization component value is compared with the corresponding polarization value. If the deviation between the two is within the preset tolerance range, the decoupling result is confirmed to be valid; otherwise, a verification failure message is output.

9. The cross-validated method for decoupling asymmetric polarization data of iron-chromium flow batteries according to claim 6, characterized in that, The transient response voltage curves used to calculate the polarization component values ​​for cross-validation are replaced with open-circuit voltage relaxation curves with millisecond-level time resolution, acquired starting when the constant current charging of the three test batteries stops.

10. The method for decoupling asymmetric polarization data of iron-chromium redox flow batteries through cross-validation according to claim 6, characterized in that, In S2, when the voltage fluctuation amplitude is within the preset threshold and the duration is not less than 30 seconds, it is determined that a steady state has been reached and the corresponding voltage data is collected. The execution sequence of constant current charging test and electrochemical impedance spectroscopy test is as follows: after the constant current charging test reaches a steady state, the electrochemical impedance spectroscopy test is executed immediately to ensure that the two sets of test data correspond to the same operating conditions.

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