Durability evaluation method and aging test system of high polymer material for flow battery

Abstract

The invention relates to a durability evaluation method and an aging test system of a high polymer material for a flow battery. According to the invention, the flow battery is adopted to carry out the aging test on the tested material, in the aging test process, the tested material is immersed in the electrolyte in the electrolyte storage tank, and the flow battery is operated according to the predetermined charging and discharging system, so that the simulation environment close to the actual service environment of the tested material is constructed, and the accuracy of the prediction result is improved; in the aging test process, the conductivity of the electrolyte in the pipeline between the electrolyte storage tank filled with the sample and the galvanic pile is detected, and the durability of the tested material in the simulation environment is represented by the conductivity change of the electrolyte, so that the test result of the aging test is accurate, and the operation is simple and convenient.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aging test, in particular to a durability evaluation method of high polymer material for flow battery and an aging test system. BACKGROUND

[0002] High polymer material has the advantages of light weight, good corrosion resistance, good chemical resistance, small conveying resistance, low price and good processability, and therefore is increasingly widely used in flow battery. At present, most of the components of flow battery, such as electrode frame, flow guide plate, bipolar plate, sealing rubber, etc., are high polymer materials. Due to the effects of long-term high temperature and electrolyte immersion, electrolyte molecules will gradually penetrate into the components of high polymer material, and with the increase of temperature and the loading of electric field, the penetration speed of organic molecules in electrolyte to high polymer material will significantly increase, thereby affecting the mechanical properties of high polymer material, and even destroying the molecular structure of the material, resulting in leakage and electric leakage of flow battery due to the failure of high polymer material in the stack.

[0003] At present, the durability research on high polymer material mainly adopts accelerated aging test method. The existing accelerated aging test method of high polymer material can only realize the superposition of 2-3 environmental factors (such as temperature, electrolyte environment), and cannot comprehensively simulate the service environment of the material, and cannot reflect the comprehensive aging effect of various factors such as working temperature, electrolyte environment and electric field encountered by high polymer material during service in flow battery, so that the durability obtained by the research has little correlation with the durability of high polymer material during service in flow battery. SUMMARY

[0004] The present application aims to overcome the deficiencies of the prior art and provide a durability evaluation method of high polymer material for flow battery and an aging test system.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0006] In a first aspect, the present application provides a durability evaluation method of high polymer material for flow battery, comprising the following steps:

[0007] S1, obtaining a sample of the measured material, dividing the sample into n groups, and using n flow batteries of the same model to perform aging test on the sample in a manner that one group of samples corresponds to one aging temperature;

[0008] The aging test comprises the following steps:

[0009] The sample is placed in an electrolyte storage tank, the electrolyte is immersed in the sample, the temperature of the electrolyte in the electrolyte storage tank is set to the corresponding aging temperature, the flow battery is operated according to a predetermined charge-discharge system, the conductivity of the electrolyte in the pipeline between the electrolyte storage tank containing the sample and the stack is monitored by using a conductivity sensor, and data of the conductivity changing with the number of charge-discharge cycles of the flow battery at different aging temperatures are obtained.

[0010] S2, constructing a service life prediction model according to the data of the conductivity changing with the number of charge-discharge cycles of the flow battery at different aging temperatures.

[0011] S3, predicting the service life of the polymer material for the flow battery by using the service life prediction model, and obtaining a service life prediction result.

[0012] Preferably, step S2 comprises:

[0013] S21, respectively, polynomial fitting the data of the conductivity changing with the number of charge-discharge cycles of the flow battery at different aging temperatures, and obtaining a relationship between the conductivity and the number of charge-discharge cycles of the flow battery at different aging temperatures.

[0014] S22, calculating the number of charge-discharge cycles of the flow battery corresponding to a preset conductivity threshold according to the relationship between the conductivity and the number of charge-discharge cycles of the flow battery at different aging temperatures, taking the calculated number of charge-discharge cycles of the flow battery as the service life of the measured material at the corresponding temperature, and obtaining data of the service life of the measured material changing with temperature.

[0015] S23, linear fitting the natural logarithm of the service life and the reciprocal of the temperature according to the data of the service life of the measured material changing with temperature, and obtaining a relationship between the natural logarithm of the service life and the reciprocal of the temperature, taking the relationship between the natural logarithm of the service life and the reciprocal of the temperature as the service life prediction model.

[0016] Further preferably, step S21 performs polynomial fitting according to a fitting formula y=a1+a2x+a3x 2 , wherein x represents the number of charge-discharge cycles of the flow battery, y represents the conductivity, a1 is a first constant, a2 is a second constant, and a3 is a third constant.

[0017] Further preferably, in step S23, the service life prediction model is lnt=b1 / T+b2, wherein t is the service life, T is the temperature, b1 is a fourth constant, and b2 is a fifth constant.

[0018] Preferably, in step S1, when it is monitored that the conductivity of the electrolyte is less than or equal to a preset conductivity threshold, the aging test is terminated.

[0019] Preferably, in step S1, the aging temperature of each group of samples is greater than the actual working temperature of the flow battery.

[0020] Preferably, in step S1, the corresponding aging temperature of the n groups of samples is different, and the difference between the corresponding aging temperatures of any two groups of samples is not less than 5K.

[0021] In this application, the temperature is the thermodynamic temperature, and the unit is Kelvin (abbreviation "open", symbol K).

[0022] Preferably, the flow battery includes any one of a vanadium flow battery, an iron-chromium flow battery, and a zinc-bromine flow battery.

[0023] Preferably, the charging and discharging system includes any one of constant current charging and discharging, constant voltage charging and discharging, constant power charging and discharging, and constant resistance charging and discharging.

[0024] Preferably, the sample of the measured material in step S1 includes at least one of polypropylene, polyethylene, polyvinyl chloride, and polypropylene glass fiber reinforced composite material.

[0025] The polypropylene glass fiber reinforced composite material can be a composite material of adding 5-40% glass fiber in polypropylene resin.

[0026] In a second aspect, the application provides an aging test system for a high molecular material of a flow battery, comprising a flow battery, wherein the flow battery comprises a stack, a positive electrode side electrolyte storage tank, an electrical conductivity sensor, a positive electrode side circulating pump, a negative electrode side electrolyte storage tank, and a negative electrode side circulating pump, the positive electrode side electrolyte storage tank is used to contain positive electrode electrolyte, the negative electrode side electrolyte storage tank is used to contain negative electrode electrolyte, the positive electrode electrolyte outlet of the stack is connected with the inlet of the positive electrode side electrolyte storage tank through a pipeline, the outlet of the positive electrode side electrolyte storage tank is connected with the positive electrode side circulating pump through a pipeline, the positive electrode side circulating pump is connected with the positive electrode electrolyte inlet of the stack through a pipeline, the positive electrode side electrolyte storage tank is provided with a temperature control device, the negative electrode electrolyte outlet of the stack is connected with the inlet of the negative electrode side electrolyte storage tank through a pipeline, the outlet of the negative electrode side electrolyte storage tank is connected with the negative electrode side circulating pump through a pipeline, and the negative electrode side circulating pump is connected with the negative electrode electrolyte inlet of the stack.

[0027] An electrical conductivity sensor is installed on the pipeline between the outlet of the positive electrode side electrolyte storage tank and the positive electrode side circulating pump.

[0028] Preferably, the aging test system for the high molecular material of the flow battery further comprises a support, a base and a support plate, wherein the base is provided with a groove, the support plate is provided with a clamping groove, and the base and the support plate are connected through a support rod.

[0029] Compared with the prior art, the application has the beneficial effects that:

[0030] The application adopts the flow battery to conduct the aging test on the measured material, in the aging test process, the measured material is immersed in the electrolyte in the electrolyte storage tank, and the flow battery is charged and discharged, so as to build a simulated environment close to the actual service environment of the measured material, and then the accuracy of the prediction result is improved.

[0031] The durability evaluation method of the polymer material for the flow battery adopts the flow battery to conduct the aging test on a group of samples corresponding to one aging temperature, in the aging test process, the conductivity of the electrolyte in the pipeline between the electrolyte storage tank containing the sample and the stack is detected, so as to obtain the data of the conductivity change with the number of charge and discharge cycles of the flow battery at different aging temperatures, and the durability of the measured material in the simulated environment is characterized by the conductivity change of the electrolyte, so that the aging test result is accurate and the operation is simple and convenient. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The application provides a structural schematic diagram of the flow battery;

[0033] Figure 2 The application provides a structural schematic diagram of the bracket;

[0034] Figure 3 The application provides a schematic diagram of the bracket inserted with the sample. DETAILED DESCRIPTION

[0035] In order to better illustrate the purpose, technical scheme and advantages of the application, the application will be further described below in combination with specific embodiments.

[0036] In the application, all directional indicators (such as up and down) are only used to explain the relative position relationship, motion condition and the like between articles in a certain specific posture (as shown in the drawings), if the specific posture changes, the directional indication also changes accordingly.

[0037] In the description of the application, it should also be noted that the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion.

[0038] For those skilled in the art, the specific meanings of the above terms in the application can be understood according to specific conditions.

[0039] It can be understood that, in the application, the temperature is a thermodynamic temperature, and the unit is K.

[0040] In a first aspect, the application provides a durability evaluation method of a polymer material for a flow battery, comprising the following steps:

[0041] S1, obtaining a sample of the measured material, dividing the sample into n groups, with one group of samples corresponding to one aging temperature, and using n liquid flow batteries of the same model to perform aging tests on the samples respectively;

[0042] The aging test comprises the following steps:

[0043] The sample is placed in an electrolyte storage tank, the electrolyte is immersed in the sample, the temperature of the electrolyte in the electrolyte storage tank is set to the corresponding aging temperature, the liquid flow battery is operated according to a predetermined charging and discharging system, and the conductivity of the electrolyte in the pipeline between the electrolyte storage tank containing the sample and the stack is monitored by using a conductivity sensor, so as to obtain data of the change of the conductivity with the number of charging and discharging cycles of the liquid flow battery at different aging temperatures;

[0044] S2, constructing a service life prediction model according to the data of the change of the conductivity with the number of charging and discharging cycles of the liquid flow battery at different aging temperatures;

[0045] S3, predicting the service life of the polymer material for liquid flow batteries by using the service life prediction model, and obtaining a service life prediction result.

[0046] The liquid flow battery is used to perform an aging test on the measured material, in the aging test process, the measured material is immersed in the electrolyte in the electrolyte storage tank, and the liquid flow battery is operated according to a predetermined charging and discharging system, so as to construct a simulated environment close to the actual service environment of the measured material, and thereby improve the accuracy of the prediction result.

[0047] The durability evaluation method of the polymer material for liquid flow batteries uses a liquid flow battery to perform an aging test on a group of samples corresponding to one aging temperature, detects the conductivity of the electrolyte in the pipeline between the electrolyte storage tank containing the sample and the stack during the aging test, and thereby obtains data of the change of the conductivity with the number of charging and discharging cycles of the liquid flow battery at different aging temperatures, so as to use the change of the conductivity of the electrolyte to represent the durability of the measured material in the simulated environment, so that the aging test result is accurate and the operation is simple and convenient.

[0048] In an embodiment, step S2 comprises:

[0049] S21, respectively, polynomial fitting the data of the change of the conductivity with the number of charging and discharging cycles of the liquid flow battery at different aging temperatures, to obtain a relationship between the conductivity and the number of charging and discharging cycles of the liquid flow battery at different aging temperatures;

[0050] S22, according to the relationship between the conductivity and the number of charge-discharge cycles of the flow battery under different aging temperatures, the number of charge-discharge cycles of the flow battery corresponding to the preset conductivity threshold is calculated when the conductivity is the preset conductivity threshold, the number of charge-discharge cycles of the flow battery calculated is the service life of the measured material at the corresponding temperature, so that the data of the service life of the measured material changing with temperature is obtained;

[0051] S23, according to the data of the service life of the measured material changing with temperature, the natural logarithm of the service life and the reciprocal of the temperature are linearly fitted to obtain the relationship between the natural logarithm of the service life and the reciprocal of the temperature, and the relationship between the natural logarithm of the service life and the reciprocal of the temperature is taken as a service life prediction model.

[0052] Specifically, step S21 is polynomial fitting according to the fitting formula y=a1+a2x+a3x 2 , wherein x represents the number of charge-discharge cycles of the flow battery, y represents the conductivity, a1 is a first constant, a2 is a second constant, and a3 is a third constant.

[0053] Specifically, the service life prediction model in step S23 is lnt=b1 / T+b2, wherein t is the service life, T is the temperature, b1 is a fourth constant, and b2 is a fifth constant.

[0054] According to the data of the change of the conductivity with the number of charge-discharge cycles of the flow battery under different aging temperatures, the service life prediction model is constructed, the service life of the polymer material for the flow battery is predicted by using the service life prediction model, and the service life prediction result is obtained, which can meet the durability evaluation demand of the polymer material in the flow battery industry.

[0055] In an embodiment, in step S1, when it is monitored that the conductivity of the electrolyte is less than or equal to the preset conductivity threshold, the aging test is terminated.

[0056] Specifically, the initial conductivity of the electrolyte before the aging test is σ0, and the preset conductivity threshold is σ m , σ m / σ0 is 0.70-0.99, for example, σ0 / σ m may be 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9, 0.95, 0.99 or a range formed by any two of the above values.

[0057] In an embodiment, in step S1, the aging temperature of each group of samples is greater than the actual working temperature of the flow battery.

[0058] In an embodiment, in step S1, the corresponding aging temperatures of the n groups of samples are different, and the difference of the corresponding aging temperatures between any two groups of samples is not less than 5K.

[0059] In an embodiment, the flow battery includes any one of a vanadium flow battery, an iron-chromium flow battery, and a zinc-bromine flow battery.

[0060] In an embodiment, the charging and discharging system includes any one of constant current charging and discharging, constant voltage charging and discharging, constant power charging and discharging, and constant resistance charging and discharging.

[0061] In an embodiment, the sample of the measured material in step S1 includes at least one of polypropylene, polyethylene, polyvinyl chloride, and polypropylene glass fiber reinforced composite material.

[0062] The polypropylene glass fiber reinforced composite material can be a composite material in which 5-40% of glass fiber is added to polypropylene resin.

[0063] It can be understood that the size of the sample is not particularly limited in the present application, and can be cut according to actual needs. For example, the sample is a cuboid, and the length is 3-20 cm and the width is 3-20 cm.

[0064] During the aging test, the sample can be first placed in the electrolyte storage tank, and then electrolyte is injected into the electrolyte storage tank. Alternatively, electrolyte can be first injected into the electrolyte storage tank, and then the sample is placed in the electrolyte storage tank.

[0065] Step S1 places the sample in the electrolyte storage tank, specifically including: inserting the sample into the clamping groove of the support, then opening the tank cover, placing the support with the sample inserted into the electrolyte storage tank, and closing the tank cover.

[0066] The material of the support is a corrosion-resistant material, such as titanium.

[0067] In a second aspect, the present application provides an aging test system for a high polymer material for a flow battery, comprising a flow battery, wherein the flow battery comprises an electric pile, a positive electrode side electrolyte storage tank, an electric conductivity sensor, a positive electrode side circulating pump, a negative electrode side electrolyte storage tank and a negative electrode side circulating pump, the positive electrode side electrolyte storage tank is used for containing positive electrode electrolyte, the negative electrode side electrolyte storage tank is used for containing negative electrode electrolyte, the positive electrode electrolyte outlet of the electric pile is connected with the inlet of the positive electrode side electrolyte storage tank through a pipeline, the outlet of the positive electrode side electrolyte storage tank is connected with the positive electrode side circulating pump through a pipeline, the positive electrode side circulating pump is connected with the positive electrode electrolyte inlet of the electric pile through a pipeline, the positive electrode side electrolyte storage tank is provided with a temperature control device, the negative electrode electrolyte outlet of the electric pile is connected with the inlet of the negative electrode side electrolyte storage tank through a pipeline, the outlet of the negative electrode side electrolyte storage tank is connected with the negative electrode side circulating pump through a pipeline, and the negative electrode side circulating pump is connected with the negative electrode electrolyte inlet of the electric pile.

[0068] An electric conductivity sensor is installed on the pipeline between the outlet of the positive electrode side electrolyte storage tank and the positive electrode side circulating pump.

[0069] In an embodiment, the outlet of the positive electrode side electrolyte storage tank and the outlet of the negative electrode side electrolyte storage tank are both provided with a filter screen.

[0070] In an embodiment, the aging test system for a high polymer material for a flow battery further comprises a support, a base and a support plate, wherein the base is provided with a recess, the support plate is provided with a clamping groove, and the base and the support plate are connected through a support rod. In use, the sample can be fixed by being inserted into the recess and the clamping groove.

[0071] The present application provides the following examples to facilitate the understanding of the present application. The present application provides these examples are not intended to limit the scope of the claims.

[0072] The specific conditions not indicated in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products that can be obtained by purchase.

[0073] Example 1

[0074] The present embodiment provides a durability evaluation method for a high polymer material for a flow battery, comprising the following steps:

[0075] S1, taking the PP glass fiber reinforced composite material provided by A company as the measured material, cutting the measured material to obtain several blocks with an area of 10 cm*20 cm as samples; the samples are divided into three groups, one group of samples corresponds to one aging temperature, and three same type of flow batteries are used to perform aging test on the samples, the aging temperatures of the three groups of samples are 313.15 K, 333.15 K and 343.15 K respectively;

[0076] The aging test comprises the following steps:

[0077] Prepare a flow battery and a bracket, the flow battery is a full vanadium flow battery, and the structure is as shown in Figure 1 The flow battery comprises a stack 1, a positive electrode side electrolyte storage tank 2, an electrical conductivity sensor 3, a positive electrode side circulating pump 4, a negative electrode side electrolyte storage tank 5 and a negative electrode side circulating pump 6, the positive electrode electrolyte outlet of the stack 1 is connected with the inlet of the positive electrode side electrolyte storage tank 2 through a pipeline, the outlet of the positive electrode side electrolyte storage tank 2 is connected with the positive electrode side circulating pump 4 through a pipeline, the positive electrode side circulating pump 4 is connected with the positive electrode electrolyte inlet of the stack 1 through a pipeline, the positive electrode side electrolyte storage tank 2 is provided with a temperature control device, the negative electrode electrolyte outlet of the stack 1 is connected with the inlet of the negative electrode side electrolyte storage tank 5 through a pipeline, the outlet of the negative electrode side electrolyte storage tank 5 is connected with the negative electrode side circulating pump 6 through a pipeline, and the negative electrode side circulating pump 6 is connected with the negative electrode electrolyte inlet of the stack 1; the outlet of the positive electrode side electrolyte storage tank 2 and the outlet of the negative electrode side electrolyte storage tank 5 are both provided with a filter screen to prevent the fragments generated by sample aging fragmentation in the aging test process from entering the stack 1;

[0078] The electrical conductivity sensor 3 is installed on the pipeline between the outlet of the positive electrode side electrolyte storage tank 2 and the positive electrode side circulating pump 4;

[0079] The structure of the bracket is as shown in Figure 2 The bracket 7 comprises a base 71 and a support plate 72, wherein the base 71 is provided with a groove 75, the support plate 72 is provided with a clamping groove 74, and the base 71 and the support plate 72 are connected through a support rod 73;

[0080] Insert the sample into the clamping groove 74 and the groove 75 of the bracket (the bracket with the sample inserted is as shown in Figure 3 , Figure 3 , wherein 8 represents the sample), then open the tank cover of the positive electrode side electrolyte storage tank 2, put the bracket with the sample fixed into the positive electrode side electrolyte storage tank 2, and close the tank cover;

[0081] The positive electrolyte is injected into the positive electrolyte storage tank 2, so that the positive electrolyte in the positive electrolyte storage tank 2 immerses the sample, and the mass ratio of the sample in the positive electrolyte storage tank 2 to the positive electrolyte is 2:1; the negative electrolyte is injected into the negative electrolyte storage tank 5; the positive electrolyte comprises the following components at the following concentrations: 2 mol / L of pentavalent vanadium ions and 4 mol / L of sulfate ions; the negative electrolyte comprises the following components at the following concentrations: 2 mol / L of divalent vanadium ions and 4 mol / L of sulfate ions.

[0082] The temperature of the electrolyte in the positive electrolyte storage tank 2 is set to the corresponding aging temperature, and the flow battery is subjected to a charge-discharge cycle (the flow rates of the positive electrolyte and the negative electrolyte are both 50 ml / min, and the current density is 200 mAcm -2 Charging is performed. After the voltage becomes 1.55 V, the charging is stopped, and then discharging is performed at 200 mAcm -2 The voltage becomes 1.0 V, the discharging is ended), the positive side circulating pump 3 and the negative side circulating pump 6 are started, so that the flow rate of the negative electrolyte in the system is the same as that of the positive electrolyte, and the conductivity sensor is used to monitor the conductivity of the electrolyte in the pipeline connected with the outlet of the positive electrolyte storage tank 2.

[0083] When the conductivity of the electrolyte is monitored to be less than or equal to the preset conductivity threshold, the aging test is terminated, so as to obtain the data of the conductivity varying with the number of charge-discharge cycles of the flow battery at different aging temperatures (as shown in Table 1); the preset conductivity threshold σ m satisfies: σ m = 0.75σ0, and σ0 is the initial conductivity of the electrolyte in the positive electrolyte storage tank 2 before the start of the aging test (i.e., the conductivity monitored when the number of charge-discharge cycles of the flow battery is 0 in Table 1);

[0084] Table 1

[0085]

[0086]

[0087] Note: " / " in Table 1 indicates that the aging test at the corresponding temperature is not performed to 6000 cycles (for example, when the number of charge-discharge cycles of the flow battery is 5500, the conductivity of the electrolyte at the corresponding temperature is less than the preset conductivity threshold, and the aging test is terminated).

[0088] S2, the data of the conductivity varying with the number of charge-discharge cycles of the flow battery at different aging temperatures are respectively subjected to polynomial fitting according to the fitting formula y = a1 + a2x + a3x 2 , to obtain the relationship between the conductivity and the number of charge-discharge cycles of the flow battery at different aging temperatures (as shown in Table 2 below).

[0089] In the fitting formula y = a1 + a2x + a3x 2 , x represents the number of charge-discharge cycles of the flow battery, y represents the conductivity, a1 is a first constant, a2 is a second constant, and a3 is a third constant.

[0090] According to the relationship between the conductivity and the number of charge-discharge cycles of the flow battery at different aging temperatures, the number of charge-discharge cycles of the flow battery corresponding to the preset conductivity threshold is calculated, and the number of charge-discharge cycles of the flow battery calculated is used as the service life of the measured material at the corresponding temperature, so that the data of the service life of the measured material changing with temperature is obtained; that is, y = σ m is substituted into the relationship between the conductivity and the number of charge-discharge cycles of the flow battery at different aging temperatures, and the following results are obtained as shown in Table 2.

[0091] Table 2

[0092]

[0093]

[0094] According to the data of the service life of the measured material changing with temperature, linear fitting is performed on lnt and 1 / T to obtain a service life prediction model: lnt = 556.43 / T + 6.9617, and the correlation coefficient R 2 is 0.9953.

[0095] S3, using the service life prediction model to predict the service life of the polymer material for the flow battery, and obtaining a service life prediction result.

[0096] In this embodiment, the service life prediction result of the measured material at a temperature of 293.15 K and in the working environment of the flow battery is: lnt = 556.43 / 293.15 + 6.9617 ≈ 8.86, t ≈ e 8.86 ≈ 7044 cycles, that is, the measured material can be charged and discharged 7044 times at a temperature of 293.15 K.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for evaluating the durability of polymer materials used in flow batteries, characterized in that, Includes the following steps: S1. Obtain a sample of the material to be tested, divide the sample into n groups, and use n identical flow batteries to conduct aging tests on the sample, with each group of samples corresponding to an aging temperature. The aging test includes the following steps: The sample is placed in an electrolyte storage tank, such that the sample is submerged in the electrolyte in the tank. The electrolyte storage tank is either the positive electrode side electrolyte storage tank or the negative electrode side electrolyte storage tank of the flow battery. The temperature of the electrolyte in the electrolyte storage tank is set to the corresponding aging temperature. The flow battery is charged and discharged. The conductivity of the electrolyte in the pipeline between the electrolyte storage tank containing the sample and the stack is monitored by a conductivity sensor. In this way, data on the change of conductivity with the number of charge and discharge cycles of the flow battery at different aging temperatures can be obtained. S2. Based on the data on the change of conductivity with the number of charge-discharge cycles of flow batteries at different aging temperatures, a service life prediction model is constructed. S3. The service life prediction model is used to predict the service life of polymer materials for flow batteries, and the service life prediction results are obtained.

2. The durability evaluation method for polymer materials used in flow batteries as described in claim 1, characterized in that, Step S2 includes: S21. Perform polynomial fitting on the data of conductivity variation with the number of charge-discharge cycles of flow battery at different aging temperatures to obtain the relationship between conductivity and the number of charge-discharge cycles of flow battery at different aging temperatures. S22. Based on the relationship between conductivity and the number of charge-discharge cycles of the flow battery at different aging temperatures, calculate the number of charge-discharge cycles of the flow battery corresponding to the preset conductivity threshold. Use the calculated number of charge-discharge cycles of the flow battery as the service life of the tested material at the corresponding temperature, thereby obtaining data on the service life of the tested material as a function of temperature. S23. Based on the data of the service life of the tested material changing with temperature, a linear fit is performed on the natural logarithm of the service life and the reciprocal of the temperature to obtain the relationship between the natural logarithm of the service life and the reciprocal of the temperature. The relationship between the natural logarithm of the service life and the reciprocal of the temperature is used as the service life prediction model.

3. The durability evaluation method for polymer materials used in flow batteries as described in claim 2, characterized in that, Step S21: According to the fitting formula y=a1+a2x+a3x 2 A polynomial fitting is performed, where x represents the number of charge-discharge cycles of the flow battery, y represents the conductivity, a1 is the first constant, a2 is the second constant, and a3 is the third constant.

4. The durability evaluation method for polymer materials used in flow batteries as described in claim 2, characterized in that, In step S23, the service life prediction model is lnt=b1 / T+b2, where t is the service life, T is the temperature, b1 is the fourth constant, and b2 is the fifth constant.

5. The durability evaluation method for polymer materials used in flow batteries as described in claim 1, characterized in that, In step S1, the aging test is terminated when the conductivity of the electrolyte is monitored to be ≤ the preset conductivity threshold.

6. The durability evaluation method for polymer materials used in flow batteries as described in claim 1, characterized in that, In step S1, the aging temperature of each group of samples is greater than the actual operating temperature of the flow battery.

7. The durability evaluation method for polymer materials used in flow batteries as described in claim 1, characterized in that, In step S1, the corresponding aging temperatures of the n groups of samples are different, and the difference between the corresponding aging temperatures of any two groups of samples is not less than 5K.

8. The durability evaluation method for polymer materials used in flow batteries as described in claim 1, characterized in that, The flow battery includes any one of the following: vanadium redox flow battery, iron-chromium flow battery, and zinc-bromine flow battery; And / or, the charge-discharge cycle method includes any one of constant current charge-discharge cycle, constant voltage charge-discharge cycle, constant power charge-discharge cycle, and constant resistance charge-discharge cycle.

9. The durability evaluation method for polymer materials used in flow batteries as described in claim 1, characterized in that, The sample of the material to be tested in step S1 includes at least one of polypropylene, polyethylene, polyvinyl chloride, and polypropylene glass fiber reinforced composite material.

10. An aging test system for polymer materials used in flow batteries, characterized in that, The invention includes a flow battery, comprising a stack, a positive-side electrolyte tank, a conductivity sensor, a positive-side circulation pump, a negative-side electrolyte tank, and a negative-side circulation pump. The positive-side electrolyte tank is used to hold positive electrolyte, and the negative-side electrolyte tank is used to hold negative electrolyte. The positive electrolyte outlet of the stack is connected to the inlet of the positive-side electrolyte tank via a pipeline. The outlet of the positive-side electrolyte tank is connected to the positive-side circulation pump via a pipeline, and the positive-side circulation pump is connected to the positive electrolyte inlet of the stack via a pipeline. The positive-side electrolyte tank is equipped with a temperature control device. The negative electrolyte outlet of the stack is connected to the inlet of the negative-side electrolyte tank via a pipeline, and the outlet of the negative-side electrolyte tank is connected to the negative-side circulation pump via a pipeline. The negative-side circulation pump is connected to the negative electrolyte inlet of the stack. A conductivity sensor is installed on the pipeline between the outlet of the positive electrode side electrolyte storage tank and the positive electrode side circulation pump.

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