A method and system for detecting the state of health of a battery in a vanadium redox flow battery energy storage system

Abstract

The present application relates to the field of liquid flow battery, in particular to a kind of battery health state detection method and system in all-vanadium liquid flow battery energy storage system.The method is first in all-vanadium liquid flow battery energy storage system Access SOH reference battery, and access electrolyte operation, then the negative electrode voltage of SOH reference battery is collected, the reaction quotient corresponding to the collected negative electrode voltage is calculated by Nernst equation, and finally the vanadium ion concentration generated by oxidation-reduction reaction in the negative electrolyte of SOH reference battery is calculated according to the reaction quotient, and the battery health state is calculated.The system includes SOH reference battery, data acquisition unit and calculation unit.The present application can effectively solve the problem of complex and low accuracy of battery health state calculation in all-vanadium liquid flow battery energy storage system, and realize the accurate calculation of battery health state in all-vanadium liquid flow battery energy storage system.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to a method and system for detecting the health status of a battery in an all-vanadium liquid flow battery energy storage system. Background Art

[0002] Clean energy, primarily solar and wind power, is currently experiencing rapid growth. However, its instability has consistently limited the further development of new energy sources. The emergence of large-scale energy storage systems has effectively improved energy utilization. Energy storage devices connect solar, wind, ocean, and hydrogen energy to the grid on a large scale, while also providing peak and frequency regulation, as well as peak-load shifting and valley-filling. Currently, traditional, large-scale energy storage technologies, such as pumped hydro storage, are unable to meet the demands of the growing new energy industry due to their demanding physical site selection and long construction cycles. Electrochemical energy storage addresses these shortcomings, offering flexible site selection and containerized storage devices that significantly shorten construction cycles. Among electrochemical energy storage batteries, flow batteries, which rely on chemical elements as the energy storage medium, offer flexible design, superior performance, recyclable electrolyte solutions, long service life, environmental friendliness, and high energy efficiency, making them ideal energy storage devices. They are commonly used in applications such as peak-load shifting and wind and solar power generation. As an efficient and reliable energy storage technology, vanadium redox flow batteries (VRFBs) offer several significant technical advantages. First, they are extremely safe. The electrolyte is a non-flammable aqueous solution, fundamentally eliminating the risk of combustion or explosion, making them particularly suitable for large-scale energy storage applications. Second, all-vanadium flow batteries offer an extremely long lifespan. During the charge and discharge process, only the vanadium ions in the electrolyte undergo valence changes; the electrode materials are not involved in the reaction. Therefore, the battery's cycle life can reach over 20 years, significantly reducing long-term maintenance and replacement costs. Furthermore, the power and capacity of all-vanadium flow batteries can be independently designed: power is determined by the size of the stack, while capacity is determined by the volume and concentration of the electrolyte. This flexibility enables customized designs to suit specific needs and diverse application scenarios. Furthermore, all-vanadium flow batteries are environmentally friendly. The electrolyte is recyclable and produces no harmful substances, meeting the requirements of green and sustainable development. Finally, their fast response time, enabling rapid switching between charge and discharge states, makes them suitable for applications requiring rapid response, such as grid frequency regulation and backup power. These technical advantages make all-vanadium flow batteries promising for large-scale energy storage, renewable energy integration, and improving grid stability.

[0003] All-vanadium redox flow batteries are affected by both external and internal factors during use. Accurately understanding the battery's state of health is essential for proper operation. Accurately estimating the battery's state of health prevents overcharging and discharging, and setting a cutoff voltage limits overcharge and overdischarge. During charge and discharge, as vanadium ions in the positive and negative electrolytes cross the ion exchange membrane, self-discharge reactions occur, gradually increasing capacity loss and causing a decrease in the state of health. Therefore, accurate state of health estimation is essential for health management of all-vanadium redox flow battery systems.

[0004] Existing techniques tend to calculate the offset between the reference voltage (RCV) and the open-circuit voltage (OCV). This offset, combined with a fitting coefficient, is used to calculate the battery system's state of health (SOH). However, this method can struggle to accurately capture local details for data with complex nonlinear relationships, especially when local extreme points exist, leading to significant calculation errors. Existing battery health testing methods for all-vanadium flow battery energy storage systems can be divided into two main categories: characteristic methods and model methods. Characteristic methods primarily include internal resistance analysis, electrochemical impedance spectroscopy (EIS), and differential analysis, while model methods primarily include aging mechanism models and probabilistic models. However, all of these methods have significant drawbacks. The difficulty with the internal resistance analysis method lies in establishing and extracting a mapping relationship between SOH and battery internal resistance. The extracted characteristic relationship is typically only applicable to a specific battery specification and has limited interoperability across different battery specifications. The EIS method involves complex EIS measurements and requires specialized instrumentation, generally limited to offline use, and similarly suffers from poor interoperability. The differential analysis method struggles to establish a mapping relationship between the peak voltage of the curve and the battery's SOH. The aging mechanism model method has problems such as large workload, long time consumption, and complex model, which makes it difficult to apply in engineering practice. The feature mapping relationship extraction of the probability model method requires considering multiple factors and is very labor-intensive.

[0005] Because all-vanadium flow battery energy storage systems generally do not fully charge and discharge during operation, it is difficult to calculate the SOH based on the actual electrical energy capacity during the partial charge and discharge process. In summary, the essence of battery aging and capacity decay is a complex, multi-factor electrochemical and physical process, and most of the real-time electrochemical parameters within the battery are difficult to accurately measure, making it difficult to accurately mathematically describe this process. The SOH calculation of all-vanadium flow batteries is affected by actual operating conditions, and the workload is huge and highly random, which increases the difficulty of calculation and makes it difficult to ensure accuracy. At the same time, the versatility of SOH estimation technology is also poor, and the results achieved so far are relatively few. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention provides a method and system for detecting the battery health status in an all-vanadium redox flow battery energy storage system. By installing an improved reference cell in the system and measuring the open-circuit voltage between different cells in the reference cell, the corresponding vanadium ion concentration in the vanadium electrolyte is obtained, and the battery health status is then determined. This method effectively addresses the complex and low-precision battery health status calculation issues in all-vanadium redox flow battery energy storage systems, enabling accurate battery health status calculation in all-vanadium redox flow battery energy storage systems.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for detecting the battery health status in an all-vanadium redox flow battery energy storage system, comprising the following steps:

[0008] S01. Connect an SOH reference battery to the all-vanadium flow battery energy storage system and connect it to the electrolyte for operation; the SOH reference battery includes a positive electrode unit, a negative electrode unit, and an intermediate unit. The positive electrode unit is connected to the positive half-cell in the all-vanadium flow battery, the negative electrode unit is connected to the negative half-cell in the all-vanadium flow battery, and the intermediate unit is independent of the all-vanadium flow battery system. A pump independent of the all-vanadium flow battery system is provided to provide electrolyte circulation power for the intermediate unit.

[0009] S02, collecting the negative electrode voltage of the SOH reference battery, and calculating the reaction quotient corresponding to the collected negative electrode voltage using the Nernst equation;

[0010] S03. Calculate the concentration of vanadium ions generated by the redox reaction in the negative electrode electrolyte of the SOH reference battery based on the reaction quotient P, and then calculate the battery health status;

[0011] Reaction Quotient ,in represents the concentration of trivalent vanadium ions generated by the redox reaction, represents the concentration of divalent vanadium ions participating in the redox reaction, A represents the ratio of ion changes in the electrolyte of the intermediate unit, and A is obtained by combining the sensor measurement value and the total ion concentration in the electrolyte of the intermediate unit. Substituting A into the reaction quotient calculation formula, we can obtain , combined with the total vanadium ion concentration at the negative electrode voltage of the SOH reference battery, we can obtain ;

[0012] The actual energy capacity of the negative electrode is calculated as follows: , where C represents the concentration of vanadium ions generated by redox reaction in the negative electrode electrolyte of the SOH reference cell, that is, , V represents the volume of the negative electrolyte of the all-vanadium redox flow battery energy storage system, z represents the number of electrons gained or lost during the reaction, and F is the Faraday constant;

[0013] Battery health status , is the actual electrical energy capacity of the negative electrode of the all-vanadium redox flow battery energy storage system, It is the maximum electrical energy capacity of the all-vanadium liquid flow battery energy storage system.

[0014] Furthermore, in step S02, the negative electrode voltage of the SOH reference battery is the potential difference between the negative electrode unit and the middle unit. The potential of the middle unit is set to 0, and the Nernst equation is expressed as:

[0015] ,

[0016] Where U is the collected negative electrode voltage of the SOH reference battery, U0 is the initial value of the negative electrode voltage of the SOH reference battery, R is the gas universal constant, T is the Kelvin temperature, F is the Faraday constant, z is the number of electrons gained or lost during the reaction, and P is the reaction quotient, that is, the ratio of the real-time concentration of the product to the real-time concentration of the reactant when the redox reaction between the negative electrode and the intermediate unit has not reached equilibrium; the reaction quotient P corresponding to the collected negative electrode voltage is calculated by the Nernst equation.

[0017] Furthermore, in step S03, the total concentration of vanadium ions at the negative electrode voltage of the SOH reference battery is measured experimentally.

[0018] Furthermore, steps S02 and S03 are performed in real time to achieve real-time monitoring of the battery health status.

[0019] Furthermore, z=1.

[0020] Furthermore, the electrolyte of the intermediate unit of the SOH reference battery is an electrolyte containing divalent and trivalent iron ions, then in step S03, the reaction quotient ,in represents the concentration of divalent iron ions generated by the redox reaction, The concentration of trivalent iron ions involved in the redox reaction is detected by a selective electrochemical sensor to detect the concentration of iron ions of a certain valence in the electrolyte of the intermediate unit. The concentration of iron ions of another valence is obtained by subtracting the concentration detected by the selective electrochemical sensor from the total concentration of iron ions in the electrolyte. 、 Substitute into the reaction quotient calculation formula to obtain , combined with the total vanadium ion concentration at the negative electrode voltage of the SOH reference battery, we can obtain .

[0021] Furthermore, the SOH reference battery includes two groups of battery cells, each group of battery cells includes a bipolar plate (1), a pole frame (2), an electrode (3), an ion exchange membrane (4) and an end plate (5), the electrode and the ion exchange membrane are arranged on the pole frame, the electrode is located on both sides of the ion exchange membrane, the bipolar plate is located at both ends of the pole frame, and the end plate is located outside the bipolar plate. The two groups of battery cells share one end plate and are connected together through the shared end plate.

[0022] Furthermore, the ion exchange membrane of the negative electrode unit is a polymer membrane based on porphyrin or calixarene.

[0023] The present invention also discloses a battery health status detection system in an all-vanadium liquid flow battery energy storage system, including a SOH reference battery, the SOH reference battery including a positive electrode unit, a negative electrode unit and an intermediate unit, the positive electrode unit is connected to the positive electrode half-cell in the all-vanadium liquid flow battery, the negative electrode unit is connected to the negative electrode half-cell in the all-vanadium liquid flow battery, the intermediate unit is independent of the all-vanadium liquid flow battery system, and is provided with a pump independent of the all-vanadium liquid flow battery system to provide electrolyte circulation power for the intermediate unit;

[0024] A data acquisition unit is used to collect the negative electrode voltage of the SOH reference battery, the total vanadium ion concentration corresponding to the negative electrode voltage of the SOH reference battery, and the electrolyte ion concentration of the intermediate unit;

[0025] The calculation unit is used to calculate the reaction quotient corresponding to the collected negative electrode voltage through the Nernst equation, and calculate the vanadium ion concentration generated by the redox reaction in the negative electrode electrolyte of the SOH reference battery based on the reaction quotient, and then calculate the battery health status.

[0026] Beneficial effects of the present invention: The present invention calculates the battery state of health SOH by measuring the concentration of vanadium ion substances through an external reference battery, which simplifies the detection process and increases the accuracy of SOH calculation through calculation. It can effectively solve the problem of complex and low accuracy of battery state of health calculation in all-vanadium liquid flow battery energy storage system, and realize accurate calculation of battery state of health in all-vanadium liquid flow battery energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of the method described in Example 1;

[0028] Figure 2 Schematic diagram of the all-vanadium redox flow battery energy storage system connected to the SOH reference battery;

[0029] Figure 3 Schematic diagram of the overall structure of the SOH reference battery;

[0030] In the figure: 1. bipolar plate, 2. pole frame, 3. electrode, 4. ion exchange membrane, 5. end plate. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] This embodiment discloses a method for detecting the battery health status in an all-vanadium redox flow battery energy storage system. Figure 1 As shown, the following steps are included:

[0034] S01. Connect the SOH reference battery to the all-vanadium redox flow battery energy storage system and connect it to the electrolyte for operation; Figure 2 As shown, the SOH reference battery includes a positive electrode unit, a negative electrode unit and an intermediate unit. The positive electrode unit is connected to the positive electrode half-cell in the all-vanadium liquid flow battery, the negative electrode unit is connected to the negative electrode half-cell in the all-vanadium liquid flow battery, and the electrolyte of the intermediate unit is an electrolyte containing divalent and trivalent iron ions, which is independent of the all-vanadium liquid flow battery system. A pump independent of the all-vanadium liquid flow battery system is provided to provide electrolyte circulation power for the intermediate unit.

[0035] S02. Collect the negative electrode voltage of the SOH reference battery, and calculate the reaction quotient corresponding to the collected negative electrode voltage using the Nernst equation.

[0036] In electrochemistry, the Nernst equation is used to calculate the equilibrium voltage of a given redox couple at an electrode relative to the standard potential. According to the Nernst equation, the voltage U1 in the SOH reference cell can be expressed as the electrolyte VO in the positive reference cell. 2+ (V 5+ ) and the intermediate reference cell electrolyte (Fe 2+ / Fe 3+ ) concentration difference, the voltage U2 can be expressed as the electrolyte VO in the negative reference unit 2+ (V 2+ ) and the intermediate reference cell electrolyte (Fe 2+ / Fe 3+ ) concentration difference. Since the positive electrode unit, negative electrode unit, and intermediate unit in the SOH reference cell have different potentials, there will be a potential difference U1 between the positive electrode unit and the intermediate unit, and a potential difference U2 between the intermediate unit and the negative electrode unit. According to the aforementioned Nernst equation, U1 and U2 are related to the ion concentration in the electrolyte. If the potential of the intermediate unit is set to 0, the total potential difference U=U1+U2 in the SOH reference cell. According to the aforementioned Nernst equation, the voltage U1 is related to the ion concentration of the electrolyte. Taking the positive electrode reference cell as an example, different ion concentrations (V 4+ / V 5+ )will have different voltage U1, when VO2+(V 5+ ) concentration increases, the voltage U1 will also increase; when VO2+(V 5+ ) concentration decreases, the voltage U1 will also decrease. The same applies to the voltage U2 in the negative reference cell.

[0037] Under the initial operating conditions, the material concentration C1 of the positive electrode vanadium ion is equal to the concentration C2 of the negative electrode vanadium ion, that is, C1=C2, but as the reaction proceeds, the vanadium ion concentration of the positive electrode will increase to C1', and the vanadium ion concentration of the negative electrode will decrease to C2'. At this time, the vanadium ion concentration in the positive and negative electrodes is C1'>C2', then the positive electrode voltage U1 will rise, and the negative electrode voltage U2 will decrease. At the same time, the sum of U1 and U2, that is, the total voltage U in the SOH reference battery, remains unchanged. Because the overflow structure set between the positive and negative electrode storage tanks in the all-vanadium liquid flow battery energy storage system can make the positive electrode electrolyte overflow into the negative electrode storage tank when the volume increases, the electrolyte volume V1 in the positive electrode storage tank and the electrolyte volume V2 in the negative electrode storage tank do not change. As the reaction proceeds, the vanadium ion concentration in the positive electrode electrolyte increases, then the amount of vanadium ion substance n in the positive electrode electrolyte 正 will increase (n 正’ =C1'×V1). Similarly, the amount of vanadium ions in the negative electrolyte will decrease accordingly. Due to the existence of the barrel effect, the actual capacity of the flow battery energy storage system depends on the side with less reactive substances in the positive and negative electrolytes. Therefore, the actual capacity depends on the energy capacity of the negative electrode. The battery health state of the flow battery SOH = Q / Q max , where Q is the actual energy capacity, Q max The maximum energy capacity of the system. The vanadium ion concentration C2' in the negative electrode can be determined by the open circuit voltage of the negative electrode unit. The vanadium ion concentration C2' in the negative electrode is correlated with the energy capacity Q of the negative electrode. At this point, the battery health status of the all-vanadium redox flow battery energy storage system can be calculated.

[0038] Specifically, in step S02, the negative electrode voltage of the SOH reference battery is the potential difference between the negative electrode unit and the middle unit. The potential of the middle unit is set to 0, and the Nernst equation is expressed as:

[0039] ,

[0040] Wherein U is the collected negative electrode voltage of the SOH reference cell, U0 is the initial value of the negative electrode voltage of the SOH reference cell, R is the gas universal constant, T is the Kelvin temperature, F is the Faraday constant, z is the number of electrons gained or lost during the reaction, and in this embodiment, z=1; P is the reaction quotient, that is, the ratio of the real-time concentration of the product to the real-time concentration of the reactant when the redox reaction between the negative electrode and the intermediate unit has not reached equilibrium; the reaction quotient P corresponding to the collected negative electrode voltage is calculated by the Nernst equation.

[0041] S03. Calculate the concentration of vanadium ions generated by the redox reaction in the negative electrode electrolyte of the SOH reference battery based on the reaction quotient P, and then calculate the battery health status.

[0042] Reaction Quotient ,in represents the concentration of trivalent vanadium ions generated by the redox reaction, represents the concentration of divalent vanadium ions participating in the redox reaction, A represents the ratio of ion changes in the electrolyte of the intermediate unit, and A is obtained by combining the sensor measurement value and the total ion concentration in the electrolyte of the intermediate unit. Substituting A into the reaction quotient calculation formula, we can obtain , combined with the total vanadium ion concentration at the negative electrode voltage of the SOH reference battery, we can obtain ; The calculation formula for the actual electric energy capacity of the negative electrode is: , where C represents the concentration of vanadium ions generated by redox reaction in the negative electrode electrolyte of the SOH reference cell, that is, , V represents the volume of the negative electrolyte of the all-vanadium redox flow battery energy storage system, z represents the number of electrons gained or lost during the reaction, in this embodiment z=1; F is the Faraday constant; battery health status , is the actual electrical energy capacity of the negative electrode of the all-vanadium redox flow battery energy storage system, It is the maximum electrical energy capacity of the all-vanadium liquid flow battery energy storage system.

[0043] In step S03, the total concentration of vanadium ions at the negative electrode voltage of the SOH reference battery is measured experimentally.

[0044] In this embodiment, steps S02 and S03 are performed in real time to achieve real-time monitoring of the battery health status.

[0045] In this embodiment, the electrolyte of the intermediate unit of the SOH reference battery is an electrolyte containing divalent and trivalent iron ions. In step S03, the reaction quotient ,in represents the concentration of divalent iron ions generated by the redox reaction, The concentration of trivalent iron ions involved in the redox reaction is detected by a selective electrochemical sensor to detect the concentration of iron ions of a certain valence in the electrolyte of the intermediate unit. The concentration of iron ions of another valence is obtained by subtracting the concentration detected by the selective electrochemical sensor from the total concentration of iron ions in the electrolyte. 、 Substitute into the reaction quotient calculation formula to obtain , combined with the total vanadium ion concentration at the negative electrode voltage of the SOH reference battery, we can obtain .

[0046] like Figure 3As shown, the SOH reference battery includes two groups of battery cells, each group of battery cells includes a bipolar plate 1, a pole frame 2, an electrode 3, an ion exchange membrane 4 and an end plate 5. The electrode 3 and the ion exchange membrane 4 are arranged on the pole frame 2, the electrode 3 is located on both sides of the ion exchange membrane 4, the bipolar plate 1 is located at both ends of the pole frame 2, and the end plate 5 is located on the outer side 1 of the bipolar plate. The two groups of battery cells share an end plate and are connected together through the shared end plate. The middle end plate, that is, the shared end plate and the electrodes 3 on both sides thereof constitute the middle unit. The part on the left side of the left ion exchange membrane 4 is the positive electrode unit, and the part on the right side of the right ion exchange membrane 4 is the negative electrode unit. In order to enable the selective electrochemical sensor to exclude the interference of vanadium ions and specifically detect iron ions, the ion exchange membrane of the negative electrode unit is a polymer membrane based on porphyrin or cup-shaped aromatic hydrocarbons, which is sensitive to Fe 3+ Have selective response.

[0047] Example 2

[0048] This embodiment discloses a battery health status detection system in an all-vanadium redox flow battery energy storage system, including a SOH reference battery. The SOH reference battery includes a positive electrode unit, a negative electrode unit, and an intermediate unit. The positive electrode unit is connected to the positive electrode half-cell in the all-vanadium redox flow battery, the negative electrode unit is connected to the negative electrode half-cell in the all-vanadium redox flow battery, and the intermediate unit is independent of the all-vanadium redox flow battery system. A pump independent of the all-vanadium redox flow battery system is provided to provide electrolyte circulation power to the intermediate unit.

[0049] A data acquisition unit is used to collect the negative electrode voltage of the SOH reference battery, the total vanadium ion concentration corresponding to the negative electrode voltage of the SOH reference battery, and the electrolyte ion concentration of the intermediate unit;

[0050] The calculation unit is used to calculate the reaction quotient corresponding to the collected negative electrode voltage through the Nernst equation, and calculate the vanadium ion concentration generated by the redox reaction in the negative electrode electrolyte of the SOH reference battery based on the reaction quotient, and then calculate the battery health status.

[0051] The above description is only the basic principle and preferred embodiments of the present invention. Improvements and substitutions made by those skilled in the art based on the present invention fall within the protection scope of the present invention.

Claims

1. A method for detecting the battery health status in an all-vanadium redox flow battery energy storage system, characterized in that: The following steps are involved: S01. Connect an SOH reference battery to the all-vanadium flow battery energy storage system and connect it to the electrolyte for operation; the SOH reference battery includes a positive electrode unit, a negative electrode unit, and an intermediate unit. The positive electrode unit is connected to the positive half-cell in the all-vanadium flow battery, the negative electrode unit is connected to the negative half-cell in the all-vanadium flow battery, and the intermediate unit is independent of the all-vanadium flow battery system. A pump independent of the all-vanadium flow battery system is provided to provide electrolyte circulation power for the intermediate unit. S02, collecting the negative electrode voltage of the SOH reference battery, and calculating the reaction quotient corresponding to the collected negative electrode voltage using the Nernst equation; S03. Calculate the concentration of vanadium ions generated by the redox reaction in the negative electrode electrolyte of the SOH reference battery based on the reaction quotient P, and then calculate the battery health status; Reaction Quotient ,in represents the concentration of trivalent vanadium ions generated by the redox reaction, represents the concentration of divalent vanadium ions participating in the redox reaction, A represents the ratio of ion changes in the electrolyte of the intermediate unit, and A is obtained by combining the sensor measurement value and the total ion concentration in the electrolyte of the intermediate unit. Substituting A into the reaction quotient calculation formula, we can obtain , combined with the total vanadium ion concentration at the negative electrode voltage of the SOH reference battery, we can obtain ; The actual energy capacity of the negative electrode is calculated as follows: , where C represents the concentration of vanadium ions generated by redox reaction in the negative electrode electrolyte of the SOH reference cell, that is, , V represents the volume of the negative electrolyte of the all-vanadium redox flow battery energy storage system, z represents the number of electrons gained or lost during the reaction, and F is the Faraday constant; Battery health status , is the actual electrical energy capacity of the negative electrode of the all-vanadium redox flow battery energy storage system, It is the maximum electrical energy capacity of the all-vanadium liquid flow battery energy storage system.

2. The method for detecting the battery health status in the all-vanadium redox flow battery energy storage system according to claim 1, characterized in that: In step S02, the negative electrode voltage of the SOH reference battery is the potential difference between the negative electrode unit and the middle unit. The potential of the middle unit is set to 0, and the Nernst equation is expressed as: ， Where U is the collected negative electrode voltage of the SOH reference battery, U0 is the initial value of the negative electrode voltage of the SOH reference battery, R is the gas universal constant, T is the Kelvin temperature, F is the Faraday constant, z is the number of electrons gained or lost during the reaction, and P is the reaction quotient, that is, the ratio of the real-time concentration of the product to the real-time concentration of the reactant when the redox reaction between the negative electrode and the intermediate unit has not reached equilibrium; the reaction quotient P corresponding to the collected negative electrode voltage is calculated using the Nernst equation.

3. The method for detecting the battery health status in the all-vanadium redox flow battery energy storage system according to claim 1, characterized in that: In step S03, the total concentration of vanadium ions at the negative electrode voltage of the SOH reference battery is measured experimentally.

4. The method for detecting the battery health status in the all-vanadium redox flow battery energy storage system according to claim 1, characterized in that: Steps S02 and S03 are performed in real time to achieve real-time monitoring of the battery health status.

5. The method for detecting the battery health status in the all-vanadium redox flow battery energy storage system according to claim 1 or 2, characterized in that: z=1。 6. The method for detecting the battery health status in the all-vanadium redox flow battery energy storage system according to claim 1, characterized in that: The electrolyte of the middle unit of the SOH reference battery is an electrolyte containing divalent and trivalent iron ions. In step S03, the reaction quotient ,in represents the concentration of divalent iron ions generated by the redox reaction, The concentration of trivalent iron ions involved in the redox reaction is detected by a selective electrochemical sensor to detect the concentration of iron ions of a certain valence in the electrolyte of the intermediate unit. The concentration of iron ions of another valence is obtained by subtracting the concentration detected by the selective electrochemical sensor from the total concentration of iron ions in the electrolyte. 、 Substitute into the reaction quotient calculation formula to obtain , combined with the total vanadium ion concentration at the negative electrode voltage of the SOH reference battery, we can obtain .

7. The method for detecting the battery health status in the all-vanadium redox flow battery energy storage system according to claim 1, characterized in that: The SOH reference battery includes two groups of battery cells, each group of battery cells includes a bipolar plate (1), a pole frame (2), an electrode (3), an ion exchange membrane (4) and an end plate (5), the electrode and the ion exchange membrane are arranged on the pole frame, the electrode is located on both sides of the ion exchange membrane, the bipolar plate is located at both ends of the pole frame, and the end plate is located outside the bipolar plate. The two groups of battery cells share an end plate and are connected together through the shared end plate.

8. The method for detecting the battery health status in the all-vanadium redox flow battery energy storage system according to claim 7, characterized in that: The ion exchange membrane of the negative electrode unit is a polymer membrane based on porphyrin or calixarene.

9. A battery health status detection system in an all-vanadium redox flow battery energy storage system, characterized by: The SOH reference battery includes a positive electrode unit, a negative electrode unit and an intermediate unit. The positive electrode unit is connected to the positive electrode half-cell in the all-vanadium liquid flow battery, the negative electrode unit is connected to the negative electrode half-cell in the all-vanadium liquid flow battery, and the intermediate unit is independent of the all-vanadium liquid flow battery system. A pump independent of the all-vanadium liquid flow battery system is provided to provide electrolyte circulation power for the intermediate unit. A data acquisition unit is used to collect the negative electrode voltage of the SOH reference battery, the total vanadium ion concentration corresponding to the negative electrode voltage of the SOH reference battery, and the electrolyte ion concentration of the intermediate unit; The calculation unit is used to calculate the reaction quotient corresponding to the collected negative electrode voltage through the Nernst equation, and calculate the vanadium ion concentration generated by the redox reaction in the negative electrode electrolyte of the SOH reference battery based on the reaction quotient, and then calculate the battery health status.

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