Online monitoring method for aging of negative electrode of iron-chromium flow battery

Abstract

The invention relates to the technical field of energy storage of iron-chromium flow batteries, and provides an online monitoring method for aging of a negative electrode of an iron-chromium flow battery. The method comprises the following steps: designing a special negative electrode storage tank system to regularly collect trace electrolyte, detecting the content of chromium complex ions Cr (H2O) 6-nCln (3-n) + (n = 0-3) through an ultraviolet spectrum, and associating cycle times to construct an aging mathematical model to form an off-line monitoring database, thereby establishing an off-line monitoring mechanism; the method comprises the following steps: establishing a special online spectrum detection experiment platform, collecting chromium complex ion spectrum data in real time, analyzing a chromium complex ion evolution rule in a charging and discharging stage and a circulating process, analyzing a dynamic behavior and a reaction mechanism of a negative electrode chromium complex ion, and establishing a battery aging online monitoring mechanism; and based on the off-line detection result and a special experimental platform, performing correlation analysis on the chromium complex ion concentration distribution trend, the chromium complex ion concentration attenuation trend and the chromium complex ion formation mechanism, and quantitatively predicting the aging time point of the battery. According to the method, offline structure-activity relationship modeling and an online spectrum analysis technology are innovatively combined, the time hysteresis limitation of traditional offline detection is broken through, and in-situ, real-time and nondestructive monitoring of the iron-chromium flow battery negative electrode aging process is realized. Meanwhile, regeneration intervention on the iron-chromium flow battery at the most appropriate time point can be effectively guided, so that the electrolyte utilization rate is maximized, the service life of the system is prolonged, and the operation and maintenance economy is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of iron-chromium liquid flow battery energy storage, and in particular to an online monitoring method for aging of an iron-chromium liquid flow battery negative electrode. Background Art

[0002] Faced with the dual challenges of fossil energy depletion and environmental pollution, the large-scale development of renewable energy has become an inevitable choice. However, its inherent intermittent and volatile characteristics will bring significant operational risks to direct grid access. Therefore, promoting the application of large-scale, long-duration energy storage technology is crucial to ensuring grid stability and improving renewable energy absorption capacity. Redox flow batteries, with their core advantages such as inherent safety, long cycle life, energy / power decoupling design, and environmental friendliness, are considered an ideal large-scale energy storage solution. Among them, all-vanadium flow batteries have the highest level of commercialization, but the high cost of vanadium resources has restricted their large-scale promotion.

[0003] Against this backdrop, iron-chromium flow batteries (Fe-CFBs) have emerged as a promising technology, leveraging their advantages in elemental abundance and potential for cost breakthroughs. Using iron (Fe), the fourth most abundant element on Earth, and chromium (Cr), the 21st most abundant, as active materials, they offer raw material costs that are only one-fifth to one-third of those of vanadium. Furthermore, their acidic aqueous electrolyte is less toxic and corrosive, significantly reducing environmental risks and operational costs. This makes Fe-Cr CFBs a strategic technology for achieving "low-cost, long-life, and scalable" energy storage, particularly suitable for grid-side 4-8 hour peak-shaving scenarios.

[0004] However, the practical application of iron-chromium flow batteries still faces key bottlenecks: the negative electrode chromium couple (Cr3 + / Cr2 + ) The sluggish reaction kinetics limits the power density and efficiency; the hydrogen evolution side reaction during charge and discharge (especially at the negative electrode) reduces the Coulombic efficiency; its aging problem is also more prominent than that of the all-vanadium system.

[0005] Therefore, it is of great significance to explore an online monitoring method for the negative electrode aging of iron-chromium flow batteries. Summary of the Invention

[0006] The purpose of the present invention is to provide an online monitoring method for the aging of the negative electrode of an iron-chromium liquid flow battery. This method designs a dedicated negative electrode electrolyte storage tank system, performs offline quantitative sampling at preset cycle nodes, and uses ultraviolet-visible spectroscopy to establish a quantitative structure-activity model of the key chromium complex ion content and spectral characteristics, and constructs a mathematical model of the evolution of the aging degree in combination with the correlation of the number of cycles. At the same time, a special online spectral detection platform is built to track the chromium complex ion spectral data in real time, analyze its evolution law, dynamic behavior and electrode interface reaction mechanism during the charge and discharge cycle, and thus realize online rapid aging status monitoring. Finally, the offline results and online platform data are integrated to conduct in-depth correlation analysis of the chromium complex ion concentration distribution / attenuation trend and its formation mechanism, so as to realize the quantitative prediction of the battery aging time point.

[0007] The present invention provides an online monitoring method for aging of the negative electrode of an iron-chromium redox flow battery, comprising:

[0008] Design a dedicated negative electrode storage tank system to regularly collect trace electrolyte and detect chromium complex ions Cr(H2O) by ultraviolet spectroscopy 6-n Cl n (3-n)+ (n=0-3) content, and the number of cycles are associated to build an aging mathematical model, forming an offline monitoring database, thereby establishing an offline monitoring mechanism;

[0009] Build a special online spectral detection experimental platform to collect real-time chromium complex ion spectral data, analyze the evolution of chromium complex ions during the charge and discharge stages and cycling process, analyze the dynamic behavior and reaction mechanism of negative electrode chromium complex ions, and establish an online monitoring mechanism for battery aging;

[0010] Based on the offline test results and the specially designed experimental platform, the distribution trend of chromium complex ion concentration, the decay trend of chromium complex ion concentration and the formation mechanism of chromium complex ions are correlated and analyzed to quantitatively predict the time point of battery aging;

[0011] According to the online monitoring method for negative electrode aging of the iron-chromium flow battery of the present invention, the dedicated negative electrode storage tank system is designed to regularly collect trace electrolyte and detect chromium complex ions Cr(H2O) by ultraviolet spectroscopy. 6-n Cl n (3-n)+ (n=0-3) content, and the number of cycles are associated to build an aging mathematical model, form an offline monitoring database, and thus establish an offline monitoring mechanism, including:

[0012] Design a dedicated negative electrode electrolyte storage tank system, extract electrolyte samples after 0-100 cycles, dilute the electrolyte samples after 0-100 cycles 100 times, and then perform UV-visible spectrum scanning in the wavelength range of 500-800nm. Finally, use the peak separation algorithm to analyze Cr(H2O)4Cl2 +、Cr(H2O)5Cl 2+ 、Cr(H2O)6 3+ Characteristic peak intensity.

[0013] Furthermore, the chromium complex ion Cr(H2O) was established 6-n Cl n (3-n)+ A quantitative structure-activity relationship model was developed between the content of (n=0-3) and the characteristic peaks of the UV spectrum. Based on the correlation analysis between the number of cycles and the change in the content of chromium complex ions, a mathematical model of the evolution of battery aging with the number of cycles was constructed to form an offline monitoring benchmark database.

[0014] According to the online monitoring method for aging of the negative electrode of an iron-chromium flow battery of the present invention, the dedicated negative electrode electrolyte storage tank system is designed to meet the requirements for extracting trace samples (single sampling volume is less than 0.5 mL).

[0015] According to the method for online monitoring of negative electrode aging of an iron-chromium redox flow battery of the present invention, a special online spectral detection experimental platform is built to collect chromium complex ion spectral data in real time, analyze the evolution of chromium complex ions during the charge and discharge stages and cycles, analyze the dynamic behavior and reaction mechanism of negative electrode chromium complex ions, and establish an online monitoring mechanism for battery aging, including:

[0016] Solution 1: While retaining the main flow channel design of the graphite plate, through local heterogeneous integration technology, the entire rectangular substrate is removed at one time through a micron-level milling process in the symmetrical areas on both sides of the flow channel, and laser-polished high-transmittance quartz monomers (transmittance > 92% @ 200-800nm) are embedded to form an integrated optical window across both sides of the flow channel.

[0017] Solution 2: Square quartz flow channels (20mm×1mm×30mm) are embedded in the electrolyte inlet and outlet pipes to replace the traditional fluororubber tubes. The high light transmittance of quartz (>92%@200-800nm) is coupled with ultraviolet-visible spectroscopy technology (purple light) to build an online rapid monitoring system.

[0018] Furthermore, a specially designed online spectral detection experimental platform for iron-chromium flow batteries enables continuous and non-destructive acquisition of dynamic UV-visible absorption spectral data of chromium complex ions in the negative electrolyte. By combining the relationship between UV absorption spectra and the content of various chromium complex ions, the evolution of various chromium complex ions during charge and discharge is determined. The dynamic behavior of negative electrode chromium complex ions during cycling is simultaneously analyzed, and the electrochemical reaction mechanism of negative electrode chromium complex ions at the electrode interface is explained, thereby establishing a rapid online monitoring mechanism for battery aging.

[0019] According to the online monitoring method for aging of the negative electrode of the iron-chromium liquid flow battery of the present invention, the width and depth of the flow channel of the main flow channel of the graphite plate should not be greater than 1 mm.

[0020] According to the online monitoring method for negative electrode aging of an iron-chromium redox flow battery of the present invention, based on the offline detection results and a specially designed experimental platform, correlation analysis is performed on the chromium complex ion concentration distribution trend, the chromium complex ion concentration decay trend and the chromium complex ion formation mechanism to quantitatively predict the battery aging time point, including:

[0021] Based on the offline detection results, the coordination evolution mechanism of chromium complex ions in the negative electrode of iron-chromium flow battery during the cycle was obtained, revealing the nature of aging. 3+ The qualitative mapping relationship between the characteristic absorption peak intensity and battery aging provides a more accurate timing trigger basis for active regeneration operations.

[0022] The present invention also provides an iron-chromium liquid flow battery that uses any one of the above-mentioned methods for online monitoring of negative electrode aging of an iron-chromium liquid flow battery to perform online monitoring of the aging of the negative electrode of the iron-chromium liquid flow battery.

[0023] The online monitoring method for the aging of the negative electrode of the iron-chromium flow battery provided by the present invention collects trace amounts of electrolyte regularly by designing a special negative electrode storage tank system, and detects the chromium complex ion Cr(H2O) by ultraviolet spectroscopy. 6-n Cl n (3-n)+ (n=0-3) content, and the number of cycles is correlated to construct an aging mathematical model, forming an offline monitoring database, thereby establishing an offline monitoring mechanism; building a special online spectral detection experimental platform, collecting chromium complex ion spectral data in real time, analyzing the evolution law of chromium complex ions during the charge and discharge stages and the cycle process, analyzing the dynamic behavior and reaction mechanism of negative electrode chromium complex ions, and establishing an online monitoring mechanism for battery aging; based on the offline detection results and the special experimental platform, the chromium complex ion concentration distribution trend, the chromium complex ion concentration decay trend and the chromium complex ion formation mechanism are correlated and analyzed to quantitatively predict the battery aging time point. The offline structure-activity relationship modeling is innovatively combined with the online spectral analysis technology, breaking through the time lag limitation of traditional offline detection, and realizing in-situ, real-time, non-destructive monitoring of the negative electrode aging process of the iron-chromium liquid flow battery. At the same time, the present invention can effectively guide the regeneration intervention of the iron-chromium liquid flow battery at the most appropriate time point, thereby maximizing the electrolyte utilization rate, extending the system life, and optimizing the operation and maintenance economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 1 is a flow chart of an online monitoring method for negative electrode aging of an iron-chromium redox flow battery provided by an embodiment of the present invention;

[0026] Figure 2 Schematic diagram of a dedicated negative electrode electrolyte storage tank system provided by an embodiment of the present invention;

[0027] Figure 3 The UV-visible peak spectra and fitted spectra of the electrolyte after 0 cycles, 1 cycle, 2 cycles, 8 cycles, 17 cycles, and 19 cycles provided by the embodiments of the present invention are shown;

[0028] Figure 4 This is a schematic diagram of the first online spectrum detection experimental platform for iron-chromium flow batteries (also known as battery testing platform 1) provided in an embodiment of the present invention;

[0029] Figure 5 This is a three-view diagram of a graphite plate of a battery cell of the first online spectrum detection experimental platform for an iron-chromium flow battery provided by an embodiment of the present invention;

[0030] Figure 6 Schematic diagram of a second online spectral detection experimental platform for iron-chromium flow batteries (also known as battery testing platform 2) provided in an embodiment of the present invention; DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] The following combination Figures 1 to 6 The present invention describes an online monitoring method for the aging of the negative electrode of an iron-chromium flow battery. Figure 1 As shown, the method includes the following steps:

[0033] S1. Design a dedicated negative electrode storage tank system to regularly collect trace electrolyte and detect chromium complex ions Cr(H2O) by ultraviolet spectroscopy. 6-n Cl n(3-n)+ (n=0-3) content, and the associated cycle number to build an aging mathematical model, form an offline monitoring database, and thus establish an offline monitoring mechanism.

[0034] In order to study the change of chromium complex ion content in the battery during charge and discharge, the present invention designed the following Figure 2 The electrolyte tank shown can analyze the change pattern of chromium complex ion content by extracting a trace amount of negative electrode electrolyte sample at a specific number of cycles, performing UV-visible spectroscopy testing, and peak separation of the UV-visible absorption spectrum.

[0035] Specifically, a UV-visible spectrophotometer was used to test the electrolyte after 0-100 cycles. Before the test, deionized water was used as a reference solution for calibration. The electrolyte sample to be tested was diluted 100 times and then scanned within the wavelength range of 500-800nm.

[0036] Furthermore, the UV-visible absorption spectrum was subjected to peak separation using OriginPro 2024. The peak separation results are shown in the figure below. Figure 3 As shown in the figure, after the first activation cycle, Cr(H2O)4Cl2 + The content of Cr(H2O)5Cl will drop rapidly. 2+ The content of Cr(H2O)6 3+ There is a slight increase, indicating that activation can increase Cr(H2O)5Cl 2+ Content (Cr(H2O)5Cl 2+ The complex layer is more easily destroyed, and the ligand is separated from the complex layer, so that the central chromium ion is directly adsorbed to the electrode surface, and an electrochemical reaction occurs), which enhances the reactivity of the chromium ion. In the subsequent charge and discharge cycles, Cr(H2O)5Cl 2 + The content of Cr(H2O)4Cl2 first increases and then tends to remain constant. + The content of Cr(H2O)6 3+ The content of Cr(H2O)6 gradually increases. This shows that the essence of electrolyte aging is Cr(H2O)6 3+ Increase in content.

[0037] Furthermore, based on this change data, combined with corresponding battery performance degradation data (such as capacity decay rate and coulombic efficiency change), and using correlation and regression analysis methods (such as linear / nonlinear fitting and time series analysis), a precise mathematical model that can quantitatively characterize the evolution of "battery aging" with "cycle number" is constructed. This model essentially describes the inherent relationship between changes in specific active material components and the macroscopic aging degree.

[0038] Furthermore, the above-mentioned spectral data obtained from samples at different cycle nodes, the chromium complex ion content information calculated by modeling, the number of cycles, the corresponding aging degree assessment value and other key information are integrated into a structured offline monitoring benchmark database.

[0039] S2. Build a special online spectral detection experimental platform to collect chromium complex ion spectral data in real time, analyze the evolution law of chromium complex ions during the charge and discharge stages and the cycle process, analyze the dynamic behavior and reaction mechanism of negative electrode chromium complex ions, and establish an online monitoring mechanism for battery aging.

[0040] In order to achieve real-time monitoring of the aging state of the iron-chromium flow battery, the method of the present invention further designs two battery testing platforms to observe the changes in the negative electrode chromium complex ions in the electrolyte.

[0041] Figure 4 Schematic diagram of the first designed Fe-Cr flow battery online spectral detection experimental platform (also known as battery testing platform 1). This battery platform redesigned the graphite plate with engraved flow channels.

[0042] Specifically, on the basis of retaining the main flow channel design of the graphite plate, through the local heterogeneous integration technology, the entire rectangular substrate is dug out at one time in the symmetrical areas on both sides of the flow channel through the micron-level milling process, and a laser-polished high-transmittance quartz monomer (transmittance> 92%, corresponding to Figure 4 Gray-bright area), forming an integrated optical window across both sides of the flow channel. Figure 5 These are three views of the graphite plate.

[0043] Furthermore, the width and depth of the flow channel of the main body of the graphite plate should not be greater than 1 mm to ensure that the thin layer of electrolyte flows to adapt to the ultraviolet-visible spectrum optical path and to ensure that the light intensity attenuation of the incident light after penetrating the electrolyte is less than 15 dB / cm.

[0044] While ensuring the mechanical and electrical properties of the graphite plates, the battery testing platform 1 opens up a new dimension for optical diagnosis of the flow channel of iron-chromium flow batteries, providing a standardized observation window solution for the next generation of smart iron-chromium flow batteries.

[0045] Figure 6 This is a schematic diagram of the second designed Fe-Cr flow battery online spectral detection experimental platform (also known as battery testing platform 2). This battery platform has redesigned pipelines.

[0046] Specifically, square quartz flow channels (20mm×1mm×30mm) are embedded in the electrolyte inlet and outlet pipes to replace traditional fluororubber tubes. The high light transmittance of quartz (>92%@200-800nm) is coupled with ultraviolet-visible spectroscopy technology (purple light) to construct an online rapid monitoring system.

[0047] Battery testing platform 2 realizes bidirectional in-situ monitoring of the negative electrode electrolyte composition at the inlet and outlet of the battery cell while maintaining the hydraulic performance and sealing reliability of the flow channel.

[0048] Using a custom-designed online spectral detection experimental platform for iron-chromium flow batteries, we can continuously and non-destructively collect dynamic UV-visible absorption spectral data of chromium complex ions in the negative electrode electrolyte. This data allows us to capture and quantify the concentration evolution of various chromium complex ions (especially key complex ions that may cause electrode passivation or capacity decay) during continuous charge and discharge cycles online with high temporal resolution, observing their dynamic changes with cycle number, charge time, and discharge time. This provides direct evidence for understanding the root causes of capacity decay, the changing trends of chromium complex ion behavior during charge and discharge, and the mechanisms of electrode interface reactions.

[0049] S3. Based on the offline detection results and the specially designed experimental platform, correlation analysis is performed on the chromium complex ion concentration distribution trend, the chromium complex ion concentration decay trend and the chromium complex ion formation mechanism to quantitatively predict the battery aging time point.

[0050] Specifically, the present invention deeply reveals the dynamic evolution behavior and internal laws of the concentration field of chromium complex ions at the negative electrode during a single charge and discharge cycle of the iron-chromium flow battery. The key discovery is that the first charge and discharge activation drives the ligand recombination (Cr(H2O)4Cl2 + →Cr(H2O)5Cl 2+ ), significantly increasing the active species Cr(H2O)5Cl 2+ The five-coordinate structure has a weak field effect of chloride ions, which leads to a decrease in the stability of the hydration layer and promotes the exposure of chromium ions (Cr 3+ ) is directly adsorbed on the electrode surface, thereby improving the charge transfer efficiency. During long-term cycling, electrolyte aging is manifested as irreversible thermodynamic relaxation: Cr(H2O)6 3+ (six-coordinate stable configuration) continues to accumulate, while the active species Cr(H2O)5Cl 2+ After the initial growth, it enters into dynamic equilibrium (±2% fluctuation). - Coordination dissociation → water molecule rearrangement → Cr(H2O)6 3+ The lattice tendency) eventually leads to an increase in the ion diffusion barrier, confirming that the essence of aging is the transformation of chromium complex ions to a high-stability, low-reactivity hydrated configuration (Cr(H2O)6 3+ ) irreversible transformation.

[0051] Furthermore, based on the exploration of the spatiotemporal evolution mechanism of concentration, the present invention innovatively designed and constructed a customized in-situ / online spectral monitoring platform. Using this platform, we can capture the key aging marker characterizing the degradation state of the negative electrode electrolyte during battery operation - Cr(H2O)6 3+ The content increased significantly.

[0052] This study reveals the evolution of the coordination structure of chromium complex ions (Cr(H2O)4Cl2 + →Cr(H2O)5Cl 2+ Improve the reaction activity, aging period Cr(H2O)6 3+ Irreversible accumulation leads to an increase in the diffusion barrier), locking the six-coordinate configuration as the essential marker of aging, and based on this, developing a method that can track Cr(H2O)6 in real time 3+ The in-situ spectral monitoring platform for iron-chromium content has achieved a breakthrough in the entire chain from microscopic mechanism analysis (breakthrough in coordination field theory) → engineering tool innovation → life management closed loop, providing both theoretical and technical support for high-precision health management and life extension strategy design of iron-chromium flow batteries.

[0053] Finally, based on the above findings and the online monitoring experimental platform, this study pioneered the construction of a "prediction system for the aging state of iron-chromium flow batteries." This system forms a complete closed-loop logic chain: "chromium complex ion formation and evolution" (triggered by microscopic chemical processes) → "precise capture of characteristic spectral signals" (real-time online non-destructive monitoring) → "critical thresholds (such as Cr(H2O)6 3+ This system provides a highly accurate and timely trigger basis for the active regeneration operation of the core electrolyte, which can effectively guide the regeneration intervention at the most appropriate time point, thereby maximizing the utilization rate of the electrolyte, extending the life of the system, and optimizing the economic efficiency of operation and maintenance.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for online monitoring of negative electrode aging of an iron-chromium redox flow battery, characterized in that: include: Design a dedicated negative electrode storage tank system to regularly collect trace electrolyte and detect chromium complex ions Cr(H2O) by ultraviolet spectroscopy 6- n Cl n (3-n)+ (n=0-3) content, and the number of cycles are associated to build an aging mathematical model, forming an offline monitoring database, thereby establishing an offline monitoring mechanism; Build a special online spectral detection experimental platform to collect real-time chromium complex ion spectral data, analyze the evolution of chromium complex ions during the charge and discharge stages and cycling process, analyze the dynamic behavior and reaction mechanism of negative electrode chromium complex ions, and establish an online monitoring mechanism for battery aging; Based on the offline detection results and the specially designed experimental platform, a correlation analysis is performed on the distribution trend of chromium complex ion concentration, the decay trend of chromium complex ion concentration and the formation mechanism of chromium complex ions to quantitatively predict the battery aging time point.

2. The method for online monitoring of negative electrode aging of an iron-chromium flow battery according to claim 1, characterized in that: The designed special negative electrode storage tank system regularly collects trace electrolyte and detects chromium complex ions Cr(H2O) by ultraviolet spectroscopy. 6-n Cl n (3-n)+ (n=0-3) content, and the number of cycles are associated to build an aging mathematical model, form an offline monitoring database, and thus establish an offline monitoring mechanism, including: Design a dedicated negative electrode electrolyte storage tank system, extract electrolyte samples after 0-100 cycles, dilute the electrolyte samples after 0-100 cycles 100 times, and then perform UV-visible spectrum scanning in the wavelength range of 500-800nm. Finally, use the peak separation algorithm to analyze Cr(H2O)4Cl2 + 、Cr(H2O)5Cl 2+ 、Cr(H2O)6 3+ Characteristic peak intensity. Furthermore, the chromium complex ion Cr(H2O) was established 6-n Cl n (3-n)+ A quantitative structure-activity relationship model was developed between the content of (n=0-3) and the characteristic peaks of the UV spectrum. Based on the correlation analysis between the number of cycles and the change in the content of chromium complex ions, a mathematical model of the evolution of battery aging with the number of cycles was constructed to form an offline monitoring benchmark database.

3. The method for online monitoring of negative electrode aging of an iron-chromium flow battery according to claim 2, characterized in that: The dedicated negative electrode electrolyte storage tank system is designed to meet the needs of micro-sample extraction (single sampling volume is less than 0.5 mL).

4. The method for online monitoring of negative electrode aging of an iron-chromium flow battery according to claim 1, wherein: The above-mentioned special online spectral detection experimental platform is built to collect chromium complex ion spectral data in real time, analyze the evolution law of chromium complex ions during the charge and discharge stages and cycles, analyze the dynamic behavior and reaction mechanism of negative electrode chromium complex ions, and establish an online monitoring mechanism for battery aging, including: Solution 1: While retaining the main flow channel design of the graphite plate, through local heterogeneous integration technology, the entire rectangular substrate is removed at one time through a micron-level milling process in the symmetrical areas on both sides of the flow channel, and laser-polished high-transmittance quartz monomers (transmittance > 92% @ 200-800nm) are embedded to form an integrated optical window across both sides of the flow channel. Solution 2: Square quartz flow channels (20mm×1mm×30mm) are embedded in the electrolyte inlet and outlet pipes to replace the traditional fluororubber tubes. The high light transmittance of quartz (>92%@200-800nm) is coupled with ultraviolet-visible spectroscopy technology (purple light) to build an online rapid monitoring system. Furthermore, a specially designed online spectral detection experimental platform for iron-chromium flow batteries enables continuous and non-destructive acquisition of dynamic UV-visible absorption spectral data of chromium complex ions in the negative electrolyte. By combining the relationship between UV absorption spectra and the content of various chromium complex ions, the evolution of various chromium complex ions during charge and discharge is determined. The dynamic behavior of negative electrode chromium complex ions during cycling is simultaneously analyzed, and the electrochemical reaction mechanism of negative electrode chromium complex ions at the electrode interface is explained, thereby establishing a rapid online monitoring mechanism for battery aging.

5. The method for online monitoring of negative electrode aging of an iron-chromium flow battery according to claim 4, characterized in that: The width and depth of the flow channel of the graphite plate main body should not be greater than 1 mm.

6. The method for online monitoring of negative electrode aging of an iron-chromium flow battery according to claim 1, characterized in that: Based on the offline test results and the specially designed experimental platform, the distribution trend of chromium complex ion concentration, the decay trend of chromium complex ion concentration and the formation mechanism of chromium complex ions are correlated and analyzed to quantitatively predict the battery aging time point, including: Based on the offline detection results, the coordination evolution mechanism of chromium complex ions in the negative electrode of iron-chromium flow battery during the cycle was obtained, revealing the nature of aging. 3+ The qualitative mapping relationship between the characteristic absorption peak intensity and battery aging provides a more accurate timing trigger basis for active regeneration operations.

7. An iron-chromium flow battery, characterized in that: An iron-chromium flow battery that uses the method for online monitoring of aging of the negative electrode of an iron-chromium flow battery as described in any one of claims 1 to 6 to perform online monitoring of aging of the negative electrode of the iron-chromium flow battery.

Images