System and method for realizing on-line detection of iron-chromium flow battery health state by decoupling asymmetric polarization data

Abstract

This invention provides a system and method for online health status monitoring of iron-chromium redox flow batteries by decoupling asymmetric polarization data. Belonging to the fields of electrochemical energy storage technology and battery state monitoring technology, the system includes a main operation module, a polarization decoupling module, and a data analysis module. Through innovative system configuration and data analysis methods, this invention achieves multi-level, quantitative decoupling of complex polarization phenomena within the battery, thereby accurately linking macroscopic state-of-the-art (SOH) degradation to microscopic electrode reactions and transport processes, providing precise and in-depth data support for battery health management.

Description

Technical Field

[0001] This invention relates to the fields of electrochemical energy storage technology and battery state monitoring technology, and in particular to a system and method for online monitoring of the health status of iron-chromium redox flow batteries by decoupling asymmetric polarization data. Background Technology

[0002] Despite the significant advantages of iron-chromium redox flow batteries, a series of technical bottlenecks remain to be addressed in their commercialization and long-term reliable operation. First, the overall performance of the battery is limited by its asymmetric electrochemical characteristics, particularly the chromium ion redox reaction on the negative electrode side. The slow charge transfer kinetics of this reaction lead to significant activation polarization, directly restricting the battery's power density and energy efficiency. Second, multiple degradation mechanisms coexist and couple over a long period, including cross-permeation of the positive and negative electrode active materials through the separator, structural aging and performance degradation of electrode materials, and contamination and decreased conductivity of the separator. This results in capacity decay and performance degradation, making the state of health (SOH) evolution process of the battery exceptionally complex and posing significant challenges to its accurate assessment, efficient operation and maintenance, and lifespan prediction.

[0003] Battery state of equilibrium (SOH) characterizes the degree of performance degradation of a battery compared to its initial state. It is a core basis for battery management systems (BMS) to optimize charge and discharge strategies, manage equalization, provide fault warnings, and predict battery life. For complex systems like iron-chromium redox flow batteries, accurate SOH assessment is particularly crucial, but also presents greater challenges. The degradation process involves changes at multiple levels, including electrochemical kinetics, mass transport, and materials science. The core difficulty in achieving accurate SOH assessment lies in deeply analyzing and quantifying the contribution of each degradation mechanism beneath the macroscopic performance degradation manifestations.

[0004] Currently, there are some research and applications on methods for evaluating the state of harmonics (SOH) of flow batteries, but all have significant limitations. The first type of method evaluates the battery based on its external macroscopic characteristics, such as monitoring changes in parameters like voltage plateau, charge / discharge capacity, energy efficiency, and coulombic efficiency during constant-current charge / discharge processes to characterize the overall performance degradation. These methods are relatively simple to operate, but only provide a comprehensive and somewhat vague SOH index, failing to reveal the intrinsic physicochemical causes of performance degradation. Furthermore, these evaluation methods typically require a complete charge-discharge cycle, which is time-consuming and difficult to meet the real-time online monitoring needs of energy storage power stations.

[0005] The second type of method is based on the measurement and analysis of battery internal resistance. An increase in internal resistance is a significant indicator of battery aging. Commonly used measurement techniques include the DC internal resistance method and electrochemical impedance spectroscopy (EIS). The DC internal resistance method quickly calculates internal resistance by applying a current pulse and measuring the voltage response, making it suitable for online applications, but it provides only a limited range of information. EIS, by applying sinusoidal perturbations of different frequencies, can obtain richer electrochemical information, including ohmic impedance, charge transfer impedance, and diffusion impedance, making it possible to analyze changes in different polarization processes. However, conventional EIS measurements obtain the overall response of the entire battery and cannot effectively separate the contributions of the positive and negative electrodes. When an increase in total internal resistance is observed, it is impossible to determine whether it is due to a decrease in the catalytic activity of the positive electrode or impaired mass transfer in the negative electrode, resulting in insufficient accuracy in fault location and diagnosis.

[0006] The third type of method is model-driven evaluation technology. This involves establishing an equivalent circuit model or a complex electrochemical mechanism model of the battery, combining this with online measurements of voltage, current, and other data for parameter identification, and then inferring the battery's state of equilibrium (SOH) by analyzing changes in internal parameters (such as resistance and capacitance). In recent years, data-driven methods combining machine learning and big data analytics have also emerged, constructing predictive models by mining degradation patterns from historical operating data. However, equivalent circuit models simplify complex electrochemical processes and lack clear physical meaning; electrochemical mechanism models are difficult to deploy online due to their complexity and enormous computational demands. Data-driven methods heavily rely on large amounts of high-quality labeled data covering the entire battery lifecycle. For iron-chromium redox flow battery systems with variable operating conditions and complex degradation modes, data acquisition costs are high, and the generalization ability and robustness of the models face challenges.

[0007] In summary, existing SOH evaluation techniques for iron-chromium redox flow batteries generally suffer from the following deep-seated problems:

[0008] 1. Vague diagnostic information and lack of localization capability. Most existing methods are "black box" tests, which can only assess the overall performance degradation of the entire cell. They cannot pinpoint the source of degradation to the positive or negative electrode, nor can they distinguish whether ohmic polarization, activation polarization, or concentration polarization is the main cause of performance deterioration. As a result, the diagnostic results cannot provide effective guidance for targeted maintenance and repair strategies.

[0009] 2. The inherent asymmetry of the battery is ignored. The ferroelectric pair at the positive electrode and the chromium pair at the negative electrode of an iron-chromium flow battery have inherent differences in reaction kinetics and reversibility. The negative electrode side is often the weakest link determining the overall performance and lifespan of the battery. However, existing evaluation methods often treat the battery as a symmetrical whole, failing to effectively decouple and distinguish the degradation contributions of the positive and negative electrodes, thus losing the ability to monitor this critical weak link.

[0010] 3. Difficulty or inaccuracy in obtaining key parameters. In iron-chromium redox flow batteries, concentration polarization is closely related to factors such as flow rate, flow channel design, and electrode pore structure due to electrolyte circulation. However, the response time constant of concentration polarization is typically tens of seconds, much longer than that of ohmic and activation polarization. Under normal dynamic operating conditions, concentration polarization is difficult to reach a steady state, and its measured value changes over time, making accurate acquisition difficult. Existing evaluation methods often ignore the influence of concentration polarization or use simplified approximations, leading to systematic distortion in the evaluation results. Summary of the Invention

[0011] This invention provides a system and method for online detection of the health status of iron-chromium redox flow batteries by decoupling asymmetric polarization data. Through innovative system configuration and data analysis methods, it achieves multi-level and quantitative decoupling of complex polarization phenomena inside the battery, thereby accurately linking macroscopic SOH degradation to microscopic electrode reactions and transport processes, providing accurate and in-depth data support for battery health management.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A system for online health status detection of iron-chromium redox flow batteries by decoupling asymmetric polarization data includes a main operation module, a polarization decoupling module, and a data analysis module.

[0014] The main operating module includes a charging and discharging battery, a positive electrode liquid tank, a negative electrode liquid tank, a PCS converter, and pumps and valves for electrolyte circulation. The PCS converter is electrically connected to the charging and discharging battery, an external power grid, or renewable energy power generation equipment.

[0015] The polarization decoupling module includes a positive electrode-side symmetrical battery, a negative electrode-side symmetrical battery, a steady-state operating battery, an electrochemical workstation, and a DC power supply. The electrolyte pipelines of the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery are all connected in parallel with the electrolyte circulation pipeline of the main operating module. The electrochemical workstation is electrically connected to the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery for conducting electrochemical impedance spectroscopy tests. The DC power supply is electrically connected to the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery for acquiring constant current charging transient voltage data.

[0016] The data analysis module is electrically connected to the polarization decoupling module, and is used to decouple and obtain the polarization parameters and open-circuit voltage of the steady-state operating battery, calculate the overall health status of the battery, decouple the internal resistance parameters of the four half-cells, and locate the degradation mechanism.

[0017] In this specification, the electrode materials, proton exchange membranes, and flow field plate structures of the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery are all consistent; both chambers of the positive electrode-side symmetrical battery are connected in parallel with the positive electrode liquid tank pipeline, both chambers of the negative electrode-side symmetrical battery are connected in parallel with the negative electrode liquid tank pipeline, and the positive electrode chamber of the steady-state operating battery is connected in parallel with the positive electrode liquid tank pipeline, and the negative electrode chamber is connected in parallel with the negative electrode liquid tank pipeline.

[0018] In this specification, the DC power supply has a millisecond-level voltage acquisition function, which is used to record the constant current charging transient response voltage curve with millisecond-level time resolution; the electrochemical workstation is used to simultaneously perform electrochemical impedance spectroscopy tests on the positive electrode side symmetrical battery, the negative electrode side symmetrical battery, and the steady-state operating battery.

[0019] In this specification, the data analysis module includes a data acquisition unit, a data preprocessing unit, a DRT analysis unit, an internal resistance and polarization decoupling unit, an internal resistance change and SOH calculation unit, a fault diagnosis knowledge base, and a human-machine interface. The data acquisition unit acquires the raw electrochemical data from the polarization decoupling module; the data preprocessing unit filters and denoises the raw data; the DRT analysis unit extracts the polarization characteristic relaxation time constant from the electrochemical impedance spectroscopy; the internal resistance and polarization decoupling unit decouples polarization and internal resistance parameters; the internal resistance change and SOH calculation unit calculates the battery health status and degradation degree; the fault diagnosis knowledge base stores the mapping relationship between degradation mechanism and parameter thresholds; and the human-machine interface is used to configure detection tasks and present diagnostic results.

[0020] In this specification, the polarization decoupling module is equipped with a synchronization control unit. The synchronization control unit is connected to the electrochemical workstation and the DC power supply signal, respectively, and is used to control the positive electrode side symmetrical battery, the negative electrode side symmetrical battery and the steady-state operation battery to start constant current charging test and electrochemical impedance spectroscopy test simultaneously, so as to ensure that the test conditions and data acquisition timing of the three batteries are completely consistent.

[0021] The method for online detection of the health status of iron-chromium redox flow batteries by decoupling asymmetric polarization data, and the system for online detection of the health status of iron-chromium redox flow batteries by decoupling asymmetric polarization data as described above, wherein the method for online detection of the health status of iron-chromium redox flow batteries by decoupling asymmetric polarization data includes:

[0022] Under a set state of charge, constant current charging was simultaneously performed on the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery, and transient response voltage curves were recorded. Electrochemical impedance spectroscopy (EIS) tests were simultaneously performed on the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery. Resistance parameters were obtained by fitting an equivalent circuit model, and polarization characteristic relaxation time constants were extracted by DRT analysis. Based on the polarization characteristic relaxation time constants and transient response voltage curves, the ohmic polarization overpotential, activation polarization overpotential, and concentration polarization overpotential of the steady-state operating battery were decoupled and calculated. Potential and total polarization overpotential; calculate the virtual steady-state voltage by combining the steady-state open-circuit voltage measured before constant current charging, and then obtain the overall health state of the battery; quantify the contribution of each polarization component to the degradation of the battery health state; calculate the concentration polarization resistance of the positive electrode side symmetrical battery, the negative electrode side symmetrical battery and the steady-state operating battery; establish a system of equations with the reversibility of the positive electrode ferroelectric pair as a constraint, and decouple to obtain the internal resistance parameters of the four half-cell reactions; based on the change of the internal resistance parameters of the half-cell reaction compared with the initial state, locate the degradation mechanism that leads to the decline of the battery health state.

[0023] In this specification, the constant current charging uses the midpoint of the current density range under actual operating conditions of the iron-chromium redox flow battery, the sampling interval of the transient response voltage curve is 1 millisecond, and the recording time covers the entire process of concentration polarization reaching steady state.

[0024] In this specification, the virtual steady-state voltage is the sum of the steady-state open-circuit voltage and the total polarization overpotential during the charging phase, and the difference between the steady-state open-circuit voltage and the total polarization overpotential during the discharging phase. The overall health status of the battery is calculated by the difference between the virtual steady-state voltage and the initial health status virtual steady-state voltage. During the calculation process, a preset attenuation threshold coefficient is used to calibrate the calculation scale of the health status.

[0025] This manual also includes the initial baseline parameter calibration steps: after the battery system is put into operation for the first time or after major maintenance is completed, a baseline state of charge is selected under preset standard operating conditions, and all testing steps are performed to obtain various parameters of the initial health state, which serve as a comparison benchmark for subsequent health state assessments.

[0026] In this manual, all testing steps are performed under multiple different states of charge, and the concentration polarization resistance of the four half-cell reactions is decoupled only at 50% charge. The parameters obtained at the current test are compared with the initial reference parameters at the same state of charge to complete the battery performance evaluation and accurately locate the degradation mechanism.

[0027] In summary, the present invention has at least the following beneficial effects:

[0028] (1) Achieving a leap in diagnostic accuracy from "macroscopic fuzziness" to "microscopic precision": For the first time, symmetrical battery design and asymmetrical battery operation were combined, and the independent parameters of the positive and negative electrodes, and even the four half-cell reactions, were successfully decoupled through mathematical models, breaking through the limitation of traditional methods that can only evaluate the overall SOH of the whole cell. Not only can the overall health status of the battery (SOH_cell) be quantified, but it can also further distinguish whether the performance degradation originates from the positive or negative electrode, and identify whether ohmic polarization, activation polarization or concentration polarization plays a dominant role, thereby achieving precise location of SOH degradation sources and in-depth insight into the degradation mechanism.

[0029] (2) Ensures the feasibility and reliability of online evaluation: The polarization decoupling module is connected in parallel with the main system, and the test process basically does not affect the operation of the main battery, realizing online or quasi-online detection. By analyzing the "virtual steady-state voltage" defined by steady-state polarization data, the problem of transient battery state changes and difficulty in evaluation under actual variable operating conditions is effectively overcome, making the SOH evaluation results more stable and reliable.

[0030] (3) Closely addressing the technical pain points of iron-chromium redox flow batteries: specifically designed to address the key issues of asymmetric positive and negative electrode kinetics and complex degradation mechanisms. By decoupling and obtaining negative electrode reaction kinetics and mass transfer parameters (such as charge transfer resistance and concentration polarization resistance), the specific modes of negative electrode performance degradation can be directly revealed. This provides high-resolution internal state data that cannot be obtained by traditional methods for the root cause analysis of core faults such as capacity decay and power reduction, thereby achieving in-depth diagnosis from phenomena to mechanisms. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the system for online detection of the health status of iron-chromium redox flow batteries by decoupling asymmetric polarization data, which is involved in this invention.

[0033] Among them, 10-main operation module; 101-charge and discharge battery; 102-positive electrode liquid tank; 103-negative electrode liquid tank; 104-PCS converter; 20-polarity decoupling module; 201-positive electrode side symmetrical battery; 202-negative electrode side symmetrical battery; 203-steady-state operation battery; 204-electrochemical workstation; 205-DC power supply; 30-data analysis module.

[0034] Figure 2 The functional architecture and data processing logic block diagram of the data analysis module provided in the embodiments of the present invention are shown below.

[0035] Figure 3 A flowchart of an online health status detection method for iron-chromium redox flow batteries provided in an embodiment of the present invention.

[0036] Figure 4 The data flow logic diagram is provided for the method of online detection of the health status of iron-chromium redox flow batteries by decoupling asymmetric polarization data, which is provided in the embodiments of the present invention.

[0037] Figure 5 This is a schematic diagram of the impedance spectrum analysis results based on relaxation time distribution (DRT) analysis in an embodiment of the present invention.

[0038] Figure 6 This is the transient response voltage curve of constant current charging in an embodiment of the present invention. Detailed Implementation

[0039] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0040] The following disclosure provides many different implementations or examples for carrying out different structures of the embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples of the embodiments of the present invention; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0041] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0042] like Figure 1 As shown, this embodiment provides a system for online detection of the health status of iron-chromium redox flow batteries by decoupling asymmetric polarization data, including a main operation module 10, a polarization decoupling module 20, and a data analysis module 30;

[0043] The main operating module 10 includes a charging and discharging battery 101, a positive electrode liquid tank 102, a negative electrode liquid tank 103, a PCS converter 104, and pumps and valves for electrolyte circulation. The PCS converter is electrically connected to the charging and discharging battery 101, the external power grid, or renewable energy power generation equipment.

[0044] The polarization decoupling module 20 includes a positive electrode-side symmetrical battery 201, a negative electrode-side symmetrical battery 202, a steady-state operating battery 203, an electrochemical workstation 204, and a DC power supply 205. The electrolyte pipelines of the positive electrode-side symmetrical battery 201, the negative electrode-side symmetrical battery 202, and the steady-state operating battery 203 are all connected in parallel with the electrolyte circulation pipeline of the main operating module 10. The electrochemical workstation 204 is electrically connected to the positive electrode-side symmetrical battery 201, the negative electrode-side symmetrical battery 202, and the steady-state operating battery 203 for conducting electrochemical impedance spectroscopy tests. The DC power supply 205 is electrically connected to the positive electrode-side symmetrical battery 201, the negative electrode-side symmetrical battery 202, and the steady-state operating battery 203 for acquiring constant current charging transient voltage data.

[0045] The data analysis module 30 is electrically connected to the polarization decoupling module 20, and is used to decouple and obtain the polarization parameters and open circuit voltage of the steady-state operating battery 203, calculate the overall health status of the battery, decouple the internal resistance parameters of the four half-cells and locate the degradation mechanism.

[0046] In some embodiments, the electrode materials, proton exchange membranes, and flow field plate structures of the positive electrode-side symmetrical battery 201, the negative electrode-side symmetrical battery 202, and the steady-state operation battery 203 are all consistent; both chambers of the positive electrode-side symmetrical battery 201 are connected in parallel with the positive electrode liquid tank 102 pipeline, both chambers of the negative electrode-side symmetrical battery 202 are connected in parallel with the negative electrode liquid tank 103 pipeline, and the positive electrode chamber of the steady-state operation battery 203 is connected in parallel with the positive electrode liquid tank 102 pipeline and the negative electrode chamber is connected in parallel with the negative electrode liquid tank 103 pipeline.

[0047] In some embodiments, the DC power supply 205 has a millisecond-level voltage acquisition function, which is used to record the constant current charging transient response voltage curve with millisecond-level time resolution; the electrochemical workstation 204 is used to simultaneously perform electrochemical impedance spectroscopy tests on the positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202 and the steady-state operating battery 203.

[0048] In some embodiments, the data analysis module 30 includes a data acquisition unit, a data preprocessing unit, a DRT analysis unit, an internal resistance and polarization decoupling unit, an internal resistance change and SOH calculation unit, a fault diagnosis knowledge base, and a human-machine interface. The data acquisition unit acquires the raw electrochemical data from the polarization decoupling module 20; the data preprocessing unit filters and denoises the raw data; the DRT analysis unit extracts the polarization characteristic relaxation time constant from the electrochemical impedance spectroscopy; the internal resistance and polarization decoupling unit decouples polarization and internal resistance parameters; the internal resistance change and SOH calculation unit calculates the battery health status and degradation degree; the fault diagnosis knowledge base stores the mapping relationship between degradation mechanism and parameter thresholds; and the human-machine interface is used to configure detection tasks and present diagnostic results.

[0049] In some embodiments, the polarization decoupling module 20 is provided with a synchronization control unit, which is connected to the electrochemical workstation 204 and the DC power supply 205 respectively. It is used to control the positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202 and the steady-state operation battery 203 to synchronously start the constant current charging test and the electrochemical impedance spectroscopy test, so as to ensure that the test conditions and data acquisition timing of the three batteries are completely consistent.

[0050] like Figure 3 As shown, a method for online detection of the health status of an iron-chromium flow battery by decoupling asymmetric polarization data is described above. The system for online detection of the health status of an iron-chromium flow battery by decoupling asymmetric polarization data, as described in any one of the above-mentioned methods, includes the following steps:

[0051] Under a set state of charge, constant current charging was simultaneously performed on the positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202, and the steady-state operating battery 203, and transient response voltage curves were recorded. Electrochemical impedance spectroscopy (EIS) tests were simultaneously performed on the positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202, and the steady-state operating battery 203. Resistance parameters were obtained by fitting an equivalent circuit model, and polarization characteristic relaxation time constants were extracted by DRT analysis. Based on the polarization characteristic relaxation time constants and transient response voltage curves, the ohmic polarization overpotential and activation polarization overpotential of the steady-state operating battery 203 were decoupled and calculated. The concentration polarization overpotential and total polarization overpotential are calculated. The virtual steady-state voltage is calculated by combining the steady-state open-circuit voltage measured before constant current charging, thereby obtaining the overall health status of the battery. The contribution of each polarization component to the degradation of the battery health status is quantified. The concentration polarization resistance of the positive electrode side symmetrical battery 201, the negative electrode side symmetrical battery 202, and the steady-state operating battery 203 are calculated. An equation system is established with the reversibility of the positive electrode ferroelectric pair as a constraint, and the internal resistance parameters of the four half-cell reactions are decoupled and obtained. Based on the change of the internal resistance parameters of the half-cell reactions compared with the initial state, the degradation mechanism that leads to the decline of the battery health status is located.

[0052] In some embodiments, the constant current charging uses the midpoint of the current density range under actual operating conditions of the iron-chromium flow battery, the sampling interval of the transient response voltage curve is 1 millisecond, and the recording time covers the entire process of concentration polarization reaching steady state.

[0053] In some embodiments, the virtual steady-state voltage is the sum of the steady-state open-circuit voltage and the total polarization overpotential during the charging phase, and the difference between the steady-state open-circuit voltage and the total polarization overpotential during the discharging phase. The overall health status of the battery is calculated by the difference between the virtual steady-state voltage and the initial health status virtual steady-state voltage. During the calculation process, a preset attenuation threshold coefficient is used to calibrate the calculation scale of the health status.

[0054] In some embodiments, an initial baseline parameter calibration step is also included: after the battery system is put into operation for the first time or after major maintenance is completed, a baseline state of charge is selected under a preset standard operating condition, and all detection steps are performed to obtain various parameters of the initial health state, which serve as a comparison benchmark for subsequent health state assessment.

[0055] In some embodiments, all detection steps are performed under multiple different states of charge, and the concentration polarization resistance of the four half-cell reactions is decoupled only under 50% charge. The parameters obtained by the current detection are compared with the initial reference parameters under the same state of charge to complete the battery performance evaluation and accurate location of the degradation mechanism.

[0056] In some embodiments, the system can be applied 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, enabling online assessment of the health status and location of degradation mechanisms for various types of flow batteries.

[0057] The technical concept of this invention is as follows:

[0058] This invention enables multi-dimensional, high-resolution diagnosis of the internal state of a battery, and can decouple the total polarization of the entire battery non-destructively and online. It can accurately separate and quantify the contributions of ohmic polarization, activation polarization, and concentration polarization, and further distinguish the kinetic characteristics and degradation states of the positive and negative electrodes, thereby achieving precise localization of the degradation mechanism. This provides key technical support for predictive maintenance of batteries, life extension, and reliable and economical operation of the overall system.

[0059] On the one hand, an online detection system is provided. This system creatively integrates a highly decoupled module 20 and a data analysis module 30 in addition to the traditional main operating module 10, which together form a collaborative diagnostic system.

[0060] The main operating module 10 is responsible for the normal energy storage and release cycle of the battery.

[0061] The polarization decoupling module 20 is a key hardware innovation of this invention. Its core comprises three identical battery cells: a steady-state operating battery 203, a positive-electrode-side symmetrical battery 201, and a negative-electrode-side symmetrical battery 202. These three batteries are connected in parallel to the electrolyte circulation system of the main operating module 10 via pipelines, ensuring that their testing environment is consistent with that of the main battery in real time. Specifically, the steady-state operating battery 203 simulates the actual operating state of the main battery; both chambers of the positive-electrode-side symmetrical battery 201 are filled with positive electrolyte, and both chambers of the negative-electrode-side symmetrical battery 202 are filled with negative electrolyte. This unique configuration lays the physical foundation for subsequent decoupling of the positive and negative electrode contributions. The module is also equipped with a high-precision electrochemical workstation 204 and a high-speed data acquisition DC power supply 205 for acquiring electrochemical impedance spectroscopy and millisecond-level transient response voltage curves.

[0062] The data analysis module 30 is the brain of this invention, responsible for processing the raw data collected by the polarization decoupling module 20. Its core function is to execute a multi-level decoupling algorithm: First, it separates ohmic polarization, activation polarization, and concentration polarization from the steady-state operating battery 203 data and calculates the overall health status (SOH_cell); then, by constructing and solving a mathematical model based on the test data of three batteries, it breaks through the decoupling of the kinetics and mass transfer parameters of the four half-cell reactions of positive electrode iron oxidation / reduction and negative electrode chromium oxidation / reduction, thereby achieving precise localization of the degradation mechanism. Specifically, the data analysis module 30 includes a data acquisition unit, a data preprocessing unit, a DRT analysis unit, an internal resistance and polarization decoupling unit, an internal resistance change and SOH calculation unit, a fault diagnosis knowledge base, and a human-machine interface. The data acquisition unit obtains raw data from the electrochemical workstation 204 and the DC power supply 205; the data preprocessing unit performs filtering and noise reduction; the DRT analysis unit extracts the characteristic relaxation time constant from the impedance spectrum; the internal resistance and polarization decoupling unit performs decoupling calculations of polarization and internal resistance; the internal resistance change and SOH calculation unit is responsible for quantifying the health status and performance degradation; the fault diagnosis knowledge base stores the mapping relationship between fault modes and parameter thresholds for mechanism localization; and the human-machine interface is used for task configuration and result presentation.

[0063] On the other hand, an online detection method using the above system is provided. The core logic of this method is "measurement-decoupling-correlation-location".

[0064] Synchronous Measurement and Feature Extraction: Under a specific state of charge, constant current excitation is simultaneously applied to the three cells in the polarization decoupling module 20, and electrochemical impedance spectroscopy is performed to simultaneously acquire their voltage transient response curves and impedance spectra. Characteristic time constants of activation polarization and concentration polarization are extracted from the impedance data through relaxation time distribution (DRT) analysis.

[0065] Full-cell polarization decoupling and SOH assessment: By utilizing the extracted characteristic time constants, the moments when different polarizations reach steady state are accurately identified from the transient voltage curves. Based on this, the ohms, activation, concentration, and total polarization overpotential of the steady-state operating battery 203 are calculated. Based on this, combined with the steady-state open-circuit voltage before constant-current charging, a "virtual steady-state voltage" independent of instantaneous operating conditions can be calculated, thereby constructing a robust quantitative index for the overall battery health state (SOH_cell). By comparing the changes in each polarization component, the main polarization types causing performance degradation can be preliminarily determined.

[0066] Half-cell reaction parameter decoupling: Based on the ohmic resistance, charge transfer resistance, and / or concentration polarization resistance obtained from the positive electrode-side symmetrical cell 201, the negative electrode-side symmetrical cell 202, and the steady-state operating cell 203, this invention constructs a dedicated decoupling method for iron-chromium redox flow batteries. The core of this algorithm is to utilize the Fe in the iron-chromium redox flow battery... 3+ / Fe 2+ The excellent electrochemical reversibility of the redox couple introduces a key physical constraint: in the symmetrical cell 201 on the positive electrode side, the ohmic resistance and charge transfer resistance of the ferrous oxidation reaction and the ferric reduction reaction can be considered equal. Based on this constraint, a system of multivariate equations is established using measured resistance data from three cells. Solving this system of equations uniquely reveals the ohmic resistance, charge transfer resistance, and / or concentration polarization resistance of each of the four half-cell reactions: ferrous oxidation at the positive electrode, ferric reduction at the ferric electrode, ferrous oxidation at the negative electrode, and ferrous oxidation at the ferric electrode.

[0067] Degradation Assessment and Mechanism Localization: By comparing the decoupled half-cell reaction parameters with their initial healthy baseline values, the performance degradation degree of each electrode reaction can be independently and quantitatively assessed. For example, a significant increase in the charge transfer resistance of the divalent chromium oxidation reaction at the negative electrode directly points to catalyst deactivation or reaction interface deterioration; while an increase in the concentration polarization resistance at the positive electrode may indicate electrode pore blockage. Ultimately, by linking the full-cell SOH degradation with changes in specific half-cell reaction parameters, the key degradation mechanisms leading to the decrease in battery SOH can be clearly identified, such as determining whether "intensified activation polarization at the negative electrode" or "deterioration of the mass transfer process at the positive electrode" is the dominant factor.

[0068] Example 1: This example describes a system for online health status detection of iron-chromium redox flow batteries by decoupling asymmetric polarization data. This system creatively integrates a main operating module 10, a dedicated polarization decoupling module 20 for diagnosis, and an intelligent data analysis module 30, constructing a hardware and software collaborative platform capable of penetrating deep into the battery's internal electrochemical processes and achieving multi-level parameter decoupling and status diagnosis.

[0069] like Figure 1 As shown, the overall architecture of the system comprises three core modules. The main operating module 10 is responsible for the normal energy storage and release cycle of the battery and is the main body of the energy storage system. The polarization decoupling module 20 is connected in parallel with the main operating module 10 through pipelines, and can acquire key electrochemical raw data for diagnosis without significantly affecting the operation of the main system. The data analysis module 30 is connected to the polarization decoupling module 20 through a data line and is responsible for processing data and outputting diagnostic results. Figure 1 The physical connections and functional logic between the modules are clearly demonstrated, reflecting the hardware integration innovation of this invention that seamlessly embeds online diagnostic functions into the operating system, laying a physical foundation for realizing online and near-online health status assessment.

[0070] The main operating module 10 includes a charge / discharge battery 101, a positive electrode electrolyte tank 102, a negative electrode electrolyte tank 103, a PCS converter 104, and supporting devices such as pumps and valves for driving electrolyte circulation. The PCS converter 104 is electrically connected to the charge / discharge battery 101, the external power grid, and / or renewable energy generation equipment to control the charging and discharging process of the charge / discharge battery 101. This module follows the conventional design of iron-chromium redox flow batteries: the positive electrode electrolyte contains Fe... 3+ / Fe 2+ Ion pairs, negative electrode electrolyte contains Cr 3+ / Cr 2+ Ion pairs are separated by an ion exchange membrane. During charging, Fe2+ ions are generated at the positive electrode. 2+ Oxidized to Fe 3+ The reaction occurs at the negative electrode, where Cr... 3+ Reduced to Cr 2+ The reaction is as follows: the discharge process is the opposite. As the energy storage and release unit, the operating status of the main operating module 10 is directly related to the economy and reliability of the entire energy storage system.

[0071] The polarization decoupling module 20 is the core hardware innovation of this invention. It includes a positive electrode-side symmetrical battery 201, a negative electrode-side symmetrical battery 202, a steady-state operating battery 203, an electrochemical workstation 204, and a DC power supply 205. The three battery units (positive electrode-side symmetrical battery 201, negative electrode-side symmetrical battery 202, and steady-state operating battery 203) have identical structures, with consistent electrode materials, proton exchange membranes, and flow field plate structures in their positive and negative chambers. This consistent design aims to eliminate measurement biases that may be introduced by structural differences and is a prerequisite for subsequent data comparison and decoupling analysis.

[0072] The fluid inlets and outlets of the positive and negative chambers of the positive electrode-side symmetrical battery 201 are connected in parallel with the circulation pipeline of the positive electrode liquid tank 102, allowing the positive electrolyte to flow through both chambers simultaneously. Correspondingly, the fluid inlets and outlets of the positive and negative chambers of the negative electrode-side symmetrical battery 202 are connected in parallel with the circulation pipeline of the negative electrode liquid tank 103, allowing the negative electrolyte to flow through both chambers simultaneously. The positive electrode chamber of the steady-state operating battery 203 is connected in parallel with the circulation pipeline of the positive electrode liquid tank 102, and its negative electrode chamber is connected in parallel with the circulation pipeline of the negative electrode liquid tank 103, thus allowing the positive and negative electrolytes to flow through their respective chambers. This parallel configuration ensures that the test environment (including electrolyte temperature, pressure, flow rate, and active material concentration) of all batteries in the polarization decoupling module 20 remains consistent with that of the main operating charge-discharge battery 101 in real-time or near real-time, fundamentally guaranteeing the representativeness and authenticity of the collected diagnostic data.

[0073] The unique design of the symmetrical battery provides a key physical basis for decoupling the contributions of the positive and negative electrodes. In the positive electrode-side symmetrical battery 201, since both chambers are filled with the same positive electrolyte, during operation, Fe2+ will inevitably occur in one chamber. 2+ Oxidation reaction occurs in one chamber, while Fe2+ reaction occurs simultaneously in another chamber. 3+ The reduction reaction occurs, and the currents in both reactions are equal in magnitude but opposite in direction. Therefore, the overall electrochemical response of this battery is essentially a linear superposition of the oxidation and reduction half-cell reactions on the positive electrode side of charge-discharge battery 101. Similarly, the overall response of the symmetrical battery 202 on the negative electrode side is the Cr reaction on the negative electrode side of charge-discharge battery 101. 2+ Oxidation and Cr 3+ The superposition of the reactions of the two half-cells is restored. The steady-state operating battery 203 realistically simulates the operating state of the main charge-discharge battery 101, and its response reflects the complete battery behavior, including contributions from both the positive and negative electrodes. By comparing and analyzing the response data of these three batteries, and utilizing Fe... 3+ / Fe 2+ The additional constraints provided by the high reversibility of the electric couple allow for the precise decoupling of the independent kinetic and mass transfer parameters of each half-cell reaction using mathematical methods.

[0074] The electrochemical workstation 204 is electrically connected to three batteries for performing electrochemical impedance spectroscopy (EIS) tests on them. During the test, the electrochemical workstation 204 applies a small-amplitude sinusoidal potential perturbation to the battery and simultaneously measures its current response, thereby obtaining an impedance spectrum containing rich information such as ohmic impedance, charge transfer impedance, and diffusion impedance.

[0075] The DC power supply 205 is a programmable power supply with millisecond-level voltage acquisition capability, and it is also electrically connected to the batteries (positive-side symmetrical battery 201, negative-side symmetrical battery 202, and steady-state operating battery 203). Its core function is to record the transient response voltage curve of the battery under constant current charging conditions, with a time resolution of milliseconds. In this process, the DC power supply 205 plays a dual role as an excitation source and a high-speed recorder: its programmable characteristics allow for precise setting of parameters such as the applied current density and duration; while its high sampling rate (e.g., a 1-millisecond sampling interval) and high-resolution data acquisition system are crucial for accurately capturing electrochemical transient processes (such as the establishment of activation polarization and concentration polarization) occurring on a millisecond to second timescale. The recording duration needs to cover the entire process from the start of current application until concentration polarization reaches a steady state, typically lasting tens of seconds, with the specific duration depending on the battery design, electrolyte flow rate, and operating current density.

[0076] The data analysis module 30 is the "brain" of this system, responsible for processing the raw data from the polarization decoupling module 20 and executing multi-level decoupling algorithms. Its functional architecture and data processing logic are as follows: Figure 2 As shown in the figure, this diagram clearly illustrates the complete process from raw data acquisition to final diagnostic result output, as well as the data flow relationships between various functional units. It is the core of understanding how this invention is realized through software hardware implementation and algorithm engineering. Figure 2 The complex analysis algorithm is systematically broken down into several clearly defined and independently implementable modular units, and the inputs, outputs and specific functions of each unit are clearly defined.

[0077] The data analysis module 30 includes a data acquisition unit, a data preprocessing unit, a DRT analysis unit, an internal resistance and polarity decoupling unit, an internal resistance change and SOH calculation unit, a fault diagnosis knowledge base, and a human-machine interface.

[0078] The data acquisition unit is responsible for acquiring raw electrochemical data from the electrochemical workstation 204 and the DC power supply 205. Specifically, this includes impedance spectral data (frequency, real and imaginary impedance values) from electrochemical impedance spectroscopy (EIS) testing and transient voltage-time curve data from constant current charging testing. This unit needs to establish a stable, high-speed communication interface with the aforementioned hardware devices to ensure the real-time performance and integrity of the data acquisition.

[0079] The data preprocessing unit is connected to the data acquisition unit, and its function is to filter and denoise the acquired raw electrochemical data. Since the raw data inevitably contains measurement noise and interference signals, effective filtering is a crucial step in improving the accuracy and reliability of subsequent analyses. Suitable filtering algorithms include moving average, wavelet denoising, or Savitzky-Golay filtering.

[0080] The DRT analysis unit is connected to the data preprocessing unit and is specifically used to perform relaxation time distribution (DRT) analysis on the preprocessed impedance spectroscopy data. DRT is a powerful electrochemical impedance spectroscopy analytical technique. Its core lies in deconvolving the complex impedance data in the frequency domain and converting it into a distribution function in the time domain (or relaxation time domain), thereby separating overlapping polarization processes. The mathematical basis of this process can be expressed by solving the following integral equation:

[0081] ;

[0082] Where Z(ω) is the measured complex impedance, R ∞Let γ be the high-frequency ohmic resistance, γ(τ) be the relaxation time distribution function to be solved, τ be the relaxation time, j be the imaginary unit, and ω be the angular frequency. Since this equation is an inverse problem and ill-conditioned, direct solutions are unstable. Regularization methods (such as Tikhonov regularization) are usually introduced to obtain stable and reliable solutions. Through DRT analysis, overlapping responses in the impedance spectrum corresponding to different physical processes can be separated along the relaxation time axis. Typically, activation polarization (originating from charge transfer processes) exhibits peaks with small time constants (on the order of milliseconds to tens of milliseconds), while concentration polarization (originating from mass diffusion processes) exhibits peaks with large time constants (on the order of seconds). Therefore, DRT analysis can clearly identify and extract the characteristic relaxation time constants (τ_act and τ_conc) corresponding to activation and concentration polarizations. This provides a crucial basis for accurately locating the steady-state or quasi-steady-state points of each polarization on the transient voltage curve.

[0083] The internal resistance and polarization decoupling unit is connected to the data preprocessing unit and the DRT analysis unit. Its core function is to perform quantitative decoupling calculations of polarization and internal resistance. This unit is the algorithm hub of this invention. By comprehensively utilizing electrochemical impedance spectroscopy (EIS) data and transient voltage curve data, and through a series of mathematical operations, it achieves two levels of decoupling: First, it decouples the ohmic polarization, activation polarization, and concentration polarization components of the steady-state operating battery 203; second, it further decouples to obtain the independent resistance parameters of the four half-cell reactions: oxidation of ferrous iron and reduction of ferric iron at the positive electrode, and oxidation of ferrous chromium and reduction of ferric chromium at the negative electrode. The specific process is as follows: First, using the characteristic relaxation time constant provided by the DRT analysis unit, the corresponding moments when activation polarization and concentration polarization reach steady state or quasi-steady state are accurately located on the transient voltage curve, and then the overpotential of each polarization is calculated. Subsequently, based on the ohmic resistance and charge transfer resistance measured from the three cells (positive electrode side symmetrical cell 201, negative electrode side symmetrical cell 202, and steady-state operation cell 203) and the calculated concentration polarization resistance, a specific set of mathematical equations is constructed and solved, ultimately resolving the independent parameters of each half-cell reaction. The calculation logic of this unit is rigorous and is a key link in realizing the leap from "macroscopic fuzzy" assessment to "microscopic precise" diagnosis.

[0084] The internal resistance change and SOH calculation unit is connected to the internal resistance and polarization decoupling unit, and its task is to quantify the battery's health state and performance degradation degree. This unit receives the decoupled parameters and compares them with pre-stored baseline parameters of the battery in its initial healthy state, calculating the change or rate of change of each parameter. Based on this, it calculates the overall health state (SOH_cell) of the battery according to the change in virtual steady-state voltage, and independently evaluates the performance degradation state of each half-cell reaction. Simultaneously, this unit is also responsible for analyzing the contribution of ohmic polarization, activation polarization, and concentration polarization to the SOH_cell degradation.

[0085] The fault diagnosis knowledge base stores preset mapping relationships between fault modes, degradation mechanisms, and specific parameter thresholds or change characteristics. This is a rule base based on expert experience, compiling common degradation modes in iron-chromium redox flow batteries (such as catalyst activity degradation, electrolyte imbalance, etc.) and their typical characteristics in electrochemical parameters (e.g., a significant increase in charge transfer resistance for a specific half-cell reaction, an abnormal increase in concentration polarization resistance, or a step change in ohmic resistance). After the internal resistance change and SOH calculation unit output quantitative evaluation results, the fault diagnosis knowledge base automatically compares the current parameter characteristics with the mapping relationships in the knowledge base through pattern matching and rule reasoning, thereby locating the specific physicochemical mechanism leading to performance degradation.

[0086] The human-machine interface serves as the window through which users interact with the entire detection system, performing the dual functions of task configuration and result presentation. Through this graphical interface, operators can easily configure detection tasks (such as setting or triggering detection) and monitor the system's operational status. More importantly, all diagnostic results, including the overall SOH_cell value of the battery, pie charts showing the contribution ratio of each polarization component, parameter change trend curves for each half-cell reaction, and the final degradation mechanism diagnostic report, are clearly and intuitively presented to the user through this interface, greatly improving the system's operability and the usability of the diagnostic results.

[0087] In summary, the system described in this embodiment, through innovative hardware integration design and modular software architecture, constructs a health status monitoring platform with online, in-situ, and high-precision diagnostic capabilities. Its core advantage lies in its successful breakthrough of the limitations of traditional "black box" evaluation methods through the physical design of the polarization decoupling module 20 and the algorithmic implementation of the data analysis module 30. This provides a systematic solution for gaining in-depth insight into the complex and asymmetric degradation state inside the battery.

[0088] Example 2: This example provides a method for online detection of the health status of iron-chromium redox flow batteries by decoupling asymmetric polarization data. The core logic of this method is "measurement-decoupling-correlation-location," which achieves accurate assessment of the health status of iron-chromium redox flow batteries and precise location of degradation mechanisms through a series of rigorous experimental steps and data analysis processes.

[0089] The execution order of the main steps of the method is as follows: Figure 3 As shown in the flowchart, the key data dependencies and computational relationships between each step are as follows: Figure 4 The data flow logic block diagram is shown below. Figure 3 and Figure 4 The two dimensions of "process steps" and "data interaction" together constitute a complete explanation of the technical solution of this method.

[0090] The method includes the following steps:

[0091] Step S1: Constant current charging transient response test.

[0092] Under a certain state of charge (SOC), the positive electrode-side symmetrical battery 201, the negative electrode-side symmetrical battery 202, and the steady-state operating battery 203 are charged with a constant current at the rated current density, and the transient response voltage curves of the three batteries are recorded simultaneously. The rated current density is usually selected as the median value of the current density range in actual operating conditions. For example, if the battery operating current density range is 40 mA / cm². 2 Up to 120mA / cm 2 Then the rated current density can be set to 80mA / cm. 2 This choice is intended to ensure that the test conditions reflect typical operating conditions, while avoiding atypical extreme polarization effects introduced by excessively high or low current densities.

[0093] To accurately capture voltage transients, the sampling interval for the voltage curve is set to 1 millisecond, while the recording duration must be sufficiently long to fully cover the entire process from the application of current until concentration polarization reaches a steady state. The establishment time of concentration polarization is affected by battery structure, electrolyte flow rate, and operating current density, typically ranging from several seconds to tens of seconds; therefore, the recording duration generally needs to last 30 to 60 seconds. The high sampling rate at the millisecond level is crucial for distinguishing polarization processes at different time scales: ohmic polarization establishes instantly upon current application, manifesting as a transient voltage jump; activation polarization establishes relatively quickly, with its characteristic time constant typically on the order of milliseconds to tens of milliseconds; while concentration polarization establishes the slowest, with its characteristic time constant reaching the order of seconds. This high-resolution time series data forms the basis for subsequent accurate separation of each polarization component based on its characteristic time constant.

[0094] Before performing the constant current charging transient response test described in step S1, an important preparatory step must be completed—initial reference parameter calibration. This method requires that this calibration step be performed after the battery system is first put into operation or after undergoing major maintenance.

[0095] The calibration is performed under preset standard operating conditions to ensure data comparability and reproducibility. Standard operating conditions typically include a specific operating temperature (e.g., 50°C), electrolyte flow rate (determined based on system design), and current density (i.e., the aforementioned rated current density, such as 80 mA / cm²). 2The calibration process includes: at one or more selected reference SOC points (e.g., 25%, 50%, 75%), performing the entire process from steps S1 to S8 to obtain and record the reference parameters of the positive electrode-side symmetrical cell 201, the negative electrode-side symmetrical cell 202, and the steady-state operating cell 203 in their initial healthy state. These parameters include: steady-state open-circuit voltage (OCV), ohmic / activation / concentration polarization overpotential, ohmic resistance, charge transfer resistance, concentration polarization resistance, and the four half-cell reactions (Fe) obtained through the decoupling algorithm. 2+ Oxidation, Fe 3+ Reduction, Cr 2+ Oxidation, Cr 3+ (Restore) the initial values ​​of each resistance component.

[0096] The complete set of initial baseline parameters recorded constitutes the battery's unique "health fingerprint," which will serve as the sole benchmark for all subsequent periodic or triggered health status assessments. This calibration step is crucial, as it establishes a reliable reference point for quantifying subsequent battery performance degradation and accurately pinpointing the degradation mechanism.

[0097] Step S2: Electrochemical impedance spectroscopy test and relaxation time distribution analysis.

[0098] At the rated current density, electrochemical impedance spectroscopy (EIS) tests were continued on the positive electrode-side symmetrical battery 201, the negative electrode-side symmetrical battery 202, and the steady-state operating battery 203. The EIS test frequency range was 10 kHz to 0.1 Hz, and a small-amplitude AC perturbation of approximately 5 mV was applied to ensure that the system response was approximately linear. Parameters such as ohmic resistance (R_ohm) and charge transfer resistance (R_ct) could be obtained by fitting an equivalent circuit model. A typical flow battery equivalent circuit includes an inductor, an ohmic resistor, a parallel resistor-capacitor unit (R_ct-C_dl) characterizing the charge transfer process, and a Warburg element describing the diffusion process. These parameters can be extracted from the impedance spectrum through nonlinear least-squares fitting.

[0099] However, equivalent circuit models have certain subjective limitations and simplification constraints. Therefore, this invention further introduces relaxation time distribution (DRT) analysis to achieve a more objective and refined analysis of the impedance spectrum. The DRT analysis results are as follows: Figure 5 As shown, this figure uses the relaxation time τ on a logarithmic scale as the abscissa and the distribution function g(τ) as the ordinate, intuitively displaying the distribution of different relaxation processes on the time scale. By separating the superimposed polarization processes in the impedance spectrum on the time axis, the DRT spectrum can clearly identify the contributions of activation polarization and concentration polarization and their relaxation times.

[0100] exist Figure 5In the DRT spectrum, four characteristic peaks can be observed, each corresponding to a different physical and electrochemical process:

[0101] The first peak corresponds to the charge transfer process (i.e., activation polarization) in the mid-frequency region. The relaxation time constant τ_act_end corresponding to the decay of its spectral peak to the tail is about 1.4 milliseconds, which indicates that the activation polarization response has reached a quasi-steady state.

[0102] The second peak corresponds to parasitic inductance in the high-frequency region and is unrelated to electrochemical reactions;

[0103] The third and fourth peaks together characterize concentration polarization. The third peak is located in the mid-to-low frequency region and originates from the transport process inside the porous electrode. The fourth peak is located in the low frequency region and reflects the semi-infinite diffusion process on the electrode surface. The relaxation time constant τ_conc_end corresponding to the decay of its spectral peak to the tail is about 18.5 seconds, indicating that the concentration polarization response has reached a quasi-steady state.

[0104] DRT analysis can accurately extract the key characteristic relaxation time constants of activation polarization and concentration polarization (1.4 ms and 18.5 s, respectively), thus providing core quantitative basis for accurately locating the steady-state time point of each polarization component on the transient voltage curve and achieving polarization separation.

[0105] Step S3: Calculation of polarization overpotential decoupling for the full cell.

[0106] This step aims to precisely decouple the total polarization overpotential of the full cell into three components: ohmic polarization, activation polarization, and concentration polarization, using the transient voltage curve obtained in step S1 and the characteristic relaxation time constant extracted in step S2. This step first performs polarization overpotential decoupling calculations on the steady-state operating cell 203. Similarly, similar calculations can be performed on the positive electrode-side symmetrical cell 201 and the negative electrode-side symmetrical cell 202 to obtain the complete polarization characteristics of each cell at a specific SOC and current density, providing data for steps S6 and S7. Taking the steady-state operating cell 203 as an example, its voltage response process during constant current charging is as follows: Figure 6 As shown in the figure, the time and voltage values ​​corresponding to the steady state or quasi-steady state of activation polarization and concentration polarization are marked.

[0107] The voltage transient response process can be divided into three stages based on its characteristic time constant:

[0108] Ohmic response phase (t=0) +): At the instant of current application, the voltage undergoes an instantaneous jump. This jump is entirely caused by the ohmic internal resistance, and the corresponding ohmic polarization overpotential is η_ohm = I·R_ohm, where R_ohm has been obtained from the EIS test, I: the battery operating current, in A (amperes), which is the real-time charge and discharge current of the iron-chromium flow battery during testing or actual operation, output by the DC power supply 205 (testing stage) or the PCS converter (operation stage). This process responds extremely quickly and is not a relaxation process, so there is no corresponding characteristic peak in the DRT spectrum. In Figure 6 this process cannot be identified separately but is included in the instantaneous jump of the voltage from the steady-state open-circuit voltage (OCV) measured before constant-current charging to point A.

[0109] Activation polarization response stage (0 < t ≤ τ_act_end): This stage corresponds to the first characteristic peak (charge transfer process) in the DRT spectrum. When the time reaches τ_act_end (about 1.4 milliseconds) extracted from the DRT analysis, the activation polarization basically reaches a steady state, and the voltage at this moment is recorded as U_act (i.e., the voltage at point A in Figure 6 ).

[0110] Concentration polarization response stage (τ_act_end < t ≤ τ_conc_end): After the activation polarization stabilizes, the concentration polarization begins to dominate the voltage change. When the time reaches τ_conc_end (about 18.5 seconds) extracted from the DRT analysis, the concentration polarization tends to a steady state, and the voltage at this moment is recorded as U_conc (i.e., the voltage at point B in Figure 6 ).

[0111] Based on the above stage division and characteristic point voltages, the calculation of each polarization overpotential component is as follows:

[0112] Concentration polarization overpotential: η_conc = U_conc - U_act;

[0113] Total polarization overpotential: η_total = U_conc - OCV;

[0114] Sum of ohmic and activation polarization overpotentials: η_ohm + act = U_act - OCV;

[0115] Ohmic polarization overpotential: η_ohm = I·R_ohm;

[0116] Activation polarization overpotential: η_act = η_ohm + act - η_ohm = U_act - OCV - I·R_ohm.

[0117] This step successfully decomposes the total polarization of the entire cell into three physically distinct components. This process is performed simultaneously on three diagnostic cells (positive electrode-side symmetrical cell 201, negative electrode-side symmetrical cell 202, and steady-state operating cell 203), thereby obtaining a complete polarization profile for each cell at a specific SOC and current density, laying the foundation for locating the sources of performance degradation in subsequent steps.

[0118] Step S4: Calculate the overall battery health status (SOH_cell).

[0119] The polarization components and total polarization value obtained from decoupling in step S3 will change as the battery ages. However, in actual variable operating conditions, the instantaneous voltage of the battery is significantly affected by current and SOC fluctuations. If the instantaneous voltage or a single polarization value is used directly to assess the health status, the results are easily affected by operating conditions. To solve this problem, this invention proposes a SOH_cell calculation method based on "virtual steady-state voltage".

[0120] The virtual steady-state voltage U_steady is defined as the terminal voltage at a specific SOC when the battery operates at its rated current density and reaches full steady state. This voltage combines the contributions of the open-circuit voltage (OCV) and the total polarization overpotential (η_total).

[0121] Charging phase: U_steady = OCV + η_total;

[0122] Discharge phase: U_steady = OCV - η_total.

[0123] U_steady is a state function that, ideally, depends only on the SOC and the battery's internal health state, and is independent of the specific dynamic path to reach that steady state. This characteristic makes it a health state indicator that is insensitive to fluctuations in operating conditions and can stably reflect the battery's intrinsic performance.

[0124] Based on this, the formula for calculating the overall battery health status (SOH_cell) is as follows:

[0125] ;

[0126] In the formula:

[0127] U_0: The virtual steady-state voltage reference value measured by the battery under the same SOC and standard operating conditions (same temperature, flow rate, and current density) when it is in its initial healthy state.

[0128] α: A preset attenuation threshold coefficient, ranging from 5% to 50%. This coefficient defines the maximum relative change range of the virtual steady-state voltage allowed when the battery life is determined to be over (i.e., SOH_cell=0). For example, if U_0=1.0V and α=20%, then when U_steady drifts to 1.0V*(1+0.2)=1.2V, SOH_cell will be calculated as 0.

[0129] The SOH_cell value, ranging from 0 to 1 (or 0% to 100%), directly reflects the degree of degradation in overall battery performance relative to its initial state. This method effectively improves the robustness and comparability of health status assessments by transforming dynamic processes into steady-state equivalent indicators.

[0130] Step S5: Quantitative analysis of the contribution of each polarization component to SOH decay.

[0131] The degradation of the overall state of health (SOH_cell) of the battery is the result of the combined effects of three components: ohmic polarization, activation polarization, and concentration polarization. To quantitatively assess the degree of degradation of each polarization process and preliminarily determine the degradation mechanism, this step performs a contribution analysis based on the polarization overpotential data obtained from decoupling in step S3.

[0132] Specifically, by comparing the polarization overpotentials measured at the evaluation time of the steady-state operating battery 203 with their corresponding values ​​under the initial health state (baseline calibration), the absolute increase of each polarization component (Δη_ohm, Δη_act, Δη_conc) can be calculated. Subsequently, the proportion of each increase in the total polarization overpotential increase can be calculated to quantify the contribution of each component to the overall SOH degradation.

[0133] Ohmic polarization contribution = Δη_ohm / Δη_total;

[0134] Activation polarization contribution = Δη_act / Δη_total;

[0135] Concentration polarization contribution = Δη_conc / Δη_total.

[0136] Δη_total: Total change in polarization overpotential. This analysis can preliminarily reveal the dominant factors in performance degradation: if the contribution of ohmic polarization is prominent, it indicates that the degradation may mainly stem from ohmic losses such as increased component contact resistance or decreased electrolyte conductivity; if the contribution of activation polarization is significant, it suggests deterioration of electrode reaction kinetics, such as loss of electrochemical active area or catalyst deactivation; if the contribution of concentration polarization is dominant, it may indicate obstruction of mass transfer processes, such as electrode pore blockage or uneven electrolyte distribution.

[0137] This quantitative analysis provides crucial directional guidance for subsequent steps that combine symmetrical cell data to accurately pinpoint the source of degradation from the "full cell degradation phenomenon" to the "root cause of degradation on a specific electrode side".

[0138] Step S6: Decompose the total internal resistance of each battery and obtain the concentration polarization resistance.

[0139] To provide a data foundation for subsequent half-cell reaction decoupling, this step requires separating the resistive component corresponding to concentration polarization from the total internal resistance of the full cell. This calculation is performed independently for the positive electrode-side symmetrical cell 201, the negative electrode-side symmetrical cell 202, and the steady-state operating cell 203.

[0140] Specifically, firstly, based on the total polarization overpotential η_total obtained in step S3 and the known operating current I, the total internal resistance R_total of the battery is calculated:

[0141] R_total = η_total / I;

[0142] Then, by subtracting the ohmic resistance R_ohm and charge transfer resistance R_ct obtained from the equivalent circuit fitting in step S2 from the total internal resistance, the concentration polarization resistance R_conc, which characterizes the degree of obstruction to the mass transfer process, can be obtained:

[0143] R_conc = R_total - R_ohm - R_ct;

[0144] Through the above calculations, each diagnostic battery obtained its three key internal resistance components: ohmic resistance, charge transfer resistance, and concentration polarization resistance. These resistance data are the core inputs for precise localization of the degradation mechanism in subsequent steps.

[0145] Step S7: Decoupling of half-cell reaction parameters.

[0146] This step is the core of the method of this invention for accurately locating the degradation mechanism. Its goal is to comprehensively utilize test data from steady-state operating battery 203 and symmetric batteries, and by establishing and solving a set of electrochemical equations, decompose the macroscopic parameters at the full-cell level into the microscopic parameters of four independent half-cell reactions.

[0147] The decoupling process is performed separately for three key components: ohmic resistance, charge transfer resistance, and concentration polarization resistance. Its principle is based on the electrochemical relationships determined by different battery configurations. Taking charge transfer resistance as an example, the charge transfer resistances of the four half-cell reactions are defined as follows:

[0148] R_ct_Fe2_ox: Oxidation reaction of ferrous iron at the positive electrode (Fe2+) 2+ →Fe 3+ +e - The charge transfer resistance of ).

[0149] R_ct_Fe3_red: Reduction reaction of ferric iron at the cathode (Fe3+) 3+ +e - →Fe 2+ The charge transfer resistance.

[0150] R_ct_Cr2_ox: Oxidation reaction of divalent chromium at the negative electrode (Cr 2+ →Cr 3+ +e - The charge transfer resistance.

[0151] R_ct_Cr3_red: Reduction reaction of trivalent chromium at the negative electrode (Cr 3+ +e - →Cr 2+ The charge transfer resistance.

[0152] Based on the different configurations of the three diagnostic batteries, the following system of equations can be established:

[0153] Equation 201 for a positive electrode side-symmetric cell: Both sides of this cell are positive electrode electrolytes, and the overall reaction can be considered as Fe... 2+ Oxidation and Fe 3+ The series connection is restored. In the AC impedance test, when a small perturbation is applied, the total charge transfer resistance R_ct_201 of the symmetrical cell satisfies:

[0154] R_ct_201=R_ct_Fe2_ox+R_ct_Fe3_red; (1)

[0155] Equation 202 for a symmetrical battery on the negative electrode side: Similarly, its total charge transfer resistance R_ct_202 satisfies:

[0156] R_ct_202=R_ct_Cr2_ox+R_ct_Cr3_red; (2)

[0157] Steady-state operating battery equation 203: The positive and negative electrodes of this battery flow through the positive and negative electrolytes respectively, and its total charge transfer resistance R_ct_203 is the series connection of the charge transfer resistance of the oxidation reaction of divalent iron at the positive electrode and the charge transfer resistance of the reduction reaction of trivalent chromium at the negative electrode:

[0158] R_ct_203=R_ct_Fe2_ox+R_ct_Cr3_red; (3)

[0159] The above four unknowns result in only three equations, requiring appropriate constraints for a solution. Therefore, this invention introduces a method based on ferroelectric pairs (Fe... 3+ / Fe 2+ The key assumption for rapid and symmetrical reaction kinetics on a carbon electrode is that the charge transfer resistance of the oxidation and reduction reactions is approximately equal, i.e.:

[0160] R_ct_Fe2_ox=R_ct_Fe3_red; (4)

[0161] This assumption simplifies equation (1) to R_ct_sym_pos=2*R_ct_Fe2_ox=2*R_ct_Fe3_red, thus allowing the parameters of the positive electrode reaction to be obtained directly from the positive electrode symmetric cell data.

[0162] Based on this, the solution process for the four unknowns can be obtained as follows:

[0163] First, R_ct_Fe2_ox and R_ct_Fe3_red are obtained directly from the positive electrode symmetric cell data:

[0164] R_ct_Fe2_ox=R_ct_Fe3_red=0.5*R_ct_201;

[0165] Then, substituting it into the equation for steady-state operation of battery 203, the negative electrode reduction reaction resistance R_ct_Cr3_red is obtained:

[0166] R_ct_Cr3_red=R_ct_203-R_ct_Fe2_ox;

[0167] Finally, substituting R_ct_Cr3_red into the equation of the negative electrode symmetrical cell (202), the negative electrode oxidation reaction resistance R_ct_Cr2_ox is obtained:

[0168] R_ct_Cr2_ox=R_ct_202-R_ct_Cr3_red;

[0169] The R_ct_201, R_ct_202, and R_ct_203 required for the above calculations are all obtained from the EIS test in step S2.

[0170] For ohmic resistors, since they also satisfy the series addition relationship, the same equation structure and solution logic can be used for decoupling. For concentration polarization resistors, decoupling is also handled under the 50% SOC condition, based on the same mathematical relationships.

[0171] Thus, this method has successfully decomposed the overall performance of the whole cell into individual electrode reaction parameters, making it possible to ultimately pinpoint the precise physicochemical root cause of performance degradation.

[0172] Step S8: Assessment of the decline state and identification of the mechanism.

[0173] The half-cell reaction resistance components obtained from decoupling in step S7 under the current state are compared with the baseline values ​​recorded under the initial healthy state. The percentage change of each component is calculated, for example:

[0174] ΔR_ct_Fe2_ox%=(R_ct_Fe2_ox_current-R_ct_Fe2_ox_init) / R_ct_Fe2_ox_init*100%;

[0175] In the formula, R_ct_Fe2_ox_current and R_ct_Fe2_ox_init are the charge transfer resistance values ​​of the oxidation reaction of ferrous iron in the current and initial healthy states, respectively; similarly, the resistance change rates of other half-cell reactions can be calculated.

[0176] These quantitative indicators reveal the degree of performance degradation of each electrode reaction. Combined with the contribution rates of each polarization type obtained in step S5, the fault diagnosis knowledge base of the data analysis module 30 begins to function, achieving precise localization of the degradation mechanism. For example:

[0177] Scenario 1: SOH_cell decreases, while ΔR_ct_Cr2_ox% and ΔR_ct_Cr3_red% increase significantly (e.g., more than 50%), while the charge transfer resistance of the iron reaction changes little, and the ohmic resistance also changes little. Knowledge base assessment: Decreased anode catalytic activity. Possible causes include irreversible passivation on the surface of the anode carbon electrode, or changes in the structure of the chromium ion complex, leading to deterioration of charge transfer kinetics. Recommendation: Check the state of the anode electrolyte; consider electrolyte regeneration or electrode activation treatment.

[0178] Scenario 2: SOH_cell decreases, with a large contribution from concentration polarization. Decoupling revealed that R_conc increased to varying degrees in all cells. Knowledge base assessment: System-level mass transfer deterioration. Possible causes: Decreased electrolyte flow rate (pump performance degradation or partial pipeline blockage), collapse of the electrode carbon felt pore structure due to long-term compression, or deposit blockage in the flow channels. Recommendation: Inspect the pump and pipeline, and analyze the electrolyte composition.

[0179] Through the above analysis, the diagnostic report can not only tell maintenance personnel that "battery performance has deteriorated", but also answer questions such as "which electrode reaction has deteriorated the most", "what type of polarization mainly causes the degradation", and "what is the most likely physicochemical root cause". This provides a direct basis for formulating precise maintenance strategies (such as electrolyte balancing, electrode activation, and component replacement), achieving a leap from "fuzzy diagnosis" to "precise positioning".

[0180] The detailed descriptions of Examples 1 and 2 fully present the specific implementation path of the system and method of the present invention. This solution, through ingenious hardware design and multi-level data decoupling algorithms, achieves for the first time a deep analysis of the asymmetric electrochemical processes inside an iron-chromium redox flow battery, elevating health status assessment from a single macroscopic indicator to multi-parameter quantification at the microscopic reaction level, providing strong technical support for intelligent operation and maintenance and extended battery life.

[0181] The embodiments described above are for illustrative purposes only and are not intended to limit the invention. Therefore, any changes in numerical values ​​or substitutions of equivalent elements should still fall within the scope of this invention.

[0182] The above detailed description will enable those skilled in the art to understand that the present invention can indeed achieve the aforementioned objectives and has complied with the provisions of the Patent Law.

[0183] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention. The above descriptions are merely preferred embodiments of the invention and are not intended to limit the invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

[0184] It should be noted that the above description of the process is for illustrative purposes only and does not limit the scope of this specification. Those skilled in the art can make various modifications and changes to the process under the guidance of this specification. However, these modifications and changes remain within the scope of this specification.

[0185] The basic concepts have been described above. Obviously, for those skilled in the art who have read this application, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore, such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of this application.

[0186] Furthermore, this application uses specific terms to describe its embodiments. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different positions in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

Claims

1. A system for online detection of the health status of iron-chromium redox flow batteries by decoupling asymmetric polarization data, characterized in that, It includes a main operating module, a polar decoupling module, and a data analysis module; The main operating module includes a charging and discharging battery, a positive electrode liquid tank, a negative electrode liquid tank, a PCS converter, and pumps and valves for electrolyte circulation. The PCS converter is electrically connected to the charging and discharging battery, an external power grid, or renewable energy power generation equipment. The polarization decoupling module includes a positive electrode-side symmetrical battery, a negative electrode-side symmetrical battery, a steady-state operating battery, an electrochemical workstation, and a DC power supply. The electrolyte pipelines of the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery are all connected in parallel with the electrolyte circulation pipeline of the main operating module. The electrochemical workstation is electrically connected to the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery for conducting electrochemical impedance spectroscopy tests. The DC power supply is electrically connected to the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery for acquiring constant current charging transient voltage data. The data analysis module is electrically connected to the polarization decoupling module, and is used to decouple and obtain the polarization parameters and open-circuit voltage of the steady-state operating battery, calculate the overall health status of the battery, decouple the internal resistance parameters of the four half-cells, and locate the degradation mechanism.

2. The system for online detection of the health status of an iron-chromium redox flow battery by decoupling asymmetric polarization data according to claim 1, characterized in that, The electrode materials, proton exchange membranes, and flow field plate structures of the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery are all consistent. Both chambers of the positive electrode-side symmetrical battery are connected in parallel with the positive electrode liquid tank pipeline, both chambers of the negative electrode-side symmetrical battery are connected in parallel with the negative electrode liquid tank pipeline, and the positive electrode chamber of the steady-state operating battery is connected in parallel with the positive electrode liquid tank pipeline, and the negative electrode chamber is connected in parallel with the negative electrode liquid tank pipeline.

3. The system for online detection of the health status of an iron-chromium redox flow battery by decoupling asymmetric polarization data according to claim 1, characterized in that, The DC power supply has a millisecond-level voltage acquisition function, which is used to record the constant current charging transient response voltage curve with millisecond-level time resolution; the electrochemical workstation is used to simultaneously conduct electrochemical impedance spectroscopy tests on the positive electrode side symmetrical battery, the negative electrode side symmetrical battery and the steady-state operating battery.

4. The system for online detection of the health status of an iron-chromium redox flow battery by decoupling asymmetric polarization data according to claim 1, characterized in that, The data analysis module includes a data acquisition unit, a data preprocessing unit, a DRT analysis unit, an internal resistance and polarization decoupling unit, an internal resistance change and SOH calculation unit, a fault diagnosis knowledge base, and a human-machine interface. The data acquisition unit acquires the raw electrochemical data from the polarization decoupling module; the data preprocessing unit filters and denoises the raw data; the DRT analysis unit extracts the polarization characteristic relaxation time constant from the electrochemical impedance spectroscopy; the internal resistance and polarization decoupling unit decouples polarization and internal resistance parameters; the internal resistance change and SOH calculation unit calculates the battery health status and degradation degree; the fault diagnosis knowledge base stores the mapping relationship between degradation mechanism and parameter thresholds; and the human-machine interface is used to configure detection tasks and present diagnostic results.

5. The system for online detection of the health status of an iron-chromium redox flow battery by decoupling asymmetric polarization data according to claim 1, characterized in that, The polarization decoupling module is equipped with a synchronization control unit, which is connected to the electrochemical workstation and the DC power supply signal respectively. It is used to control the positive electrode side symmetrical battery, the negative electrode side symmetrical battery and the steady-state operation battery to start constant current charging test and electrochemical impedance spectroscopy test simultaneously, so as to ensure that the test conditions and data acquisition timing of the three batteries are completely consistent.

6. A method for online detection of the health status of an iron-chromium redox flow battery by decoupling asymmetric polarization data, characterized in that, The system for online detection of the health status of an iron-chromium flow battery by decoupling asymmetric polarization data, as described in any one of claims 1 to 5, wherein the method for online detection of the health status of an iron-chromium flow battery by decoupling asymmetric polarization data comprises: Under a set state of charge, constant current charging was simultaneously performed on the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery, and transient response voltage curves were recorded. Electrochemical impedance spectroscopy (EIS) tests were simultaneously performed on the positive electrode-side symmetrical battery, the negative electrode-side symmetrical battery, and the steady-state operating battery. Resistance parameters were obtained by fitting an equivalent circuit model, and polarization characteristic relaxation time constants were extracted by DRT analysis. Based on the polarization characteristic relaxation time constants and transient response voltage curves, the ohmic polarization overpotential, activation polarization overpotential, and concentration polarization overpotential of the steady-state operating battery were decoupled and calculated. Potential and total polarization overpotential; calculate the virtual steady-state voltage by combining the steady-state open-circuit voltage measured before constant current charging, and then obtain the overall health state of the battery; quantify the contribution of each polarization component to the degradation of the battery health state; calculate the concentration polarization resistance of the positive electrode side symmetrical battery, the negative electrode side symmetrical battery and the steady-state operating battery; establish a system of equations with the reversibility of the positive electrode ferroelectric pair as a constraint, and decouple to obtain the internal resistance parameters of the four half-cell reactions; based on the change of the internal resistance parameters of the half-cell reaction compared with the initial state, locate the degradation mechanism that leads to the decline of the battery health state.

7. The method for online detection of the health status of an iron-chromium redox flow battery by decoupling asymmetric polarization data according to claim 6, characterized in that, The constant current charging uses the midpoint of the current density range under actual operating conditions of the iron-chromium flow battery. The sampling interval of the transient response voltage curve is 1 millisecond, and the recording time covers the entire process of concentration polarization reaching steady state.

8. The method for online detection of the health status of an iron-chromium redox flow battery by decoupling asymmetric polarization data according to claim 6, characterized in that, The virtual steady-state voltage is the sum of the steady-state open-circuit voltage and the total polarization overpotential during the charging phase, and the difference between the steady-state open-circuit voltage and the total polarization overpotential during the discharging phase. The overall health status of the battery is calculated by the difference between the virtual steady-state voltage and the initial health status virtual steady-state voltage. During the calculation, a preset attenuation threshold coefficient is used to calibrate the calculation scale of the health status.

9. The method for online detection of the health status of an iron-chromium redox flow battery by decoupling asymmetric polarization data according to claim 6, characterized in that, It also includes an initial baseline parameter calibration step: after the battery system is put into operation for the first time or after major maintenance, a baseline state of charge is selected under preset standard operating conditions, and all testing steps are performed to obtain various parameters of the initial health state, which serve as a comparison benchmark for subsequent health state assessments.

10. The method for online detection of the health status of an iron-chromium redox flow battery by decoupling asymmetric polarization data according to claim 6, characterized in that, All detection steps are performed under multiple different states of charge, and the concentration polarization resistance of the four half-cell reactions is decoupled only under 50% charge. The parameters obtained at the current detection are compared with the initial benchmark parameters under the same state of charge to complete the battery performance evaluation and accurately locate the degradation mechanism.

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