Method for evaluating durability of polymer material for liquid flow battery and aging test system

Abstract

The application relates to a durability evaluation method and an aging test system of a high polymer material for a liquid flow battery. The application adopts a liquid flow battery to conduct an aging test on a measured material. In the aging test process, the measured material is immersed in electrolyte in an electrolyte storage tank, and the liquid flow battery is operated according to a predetermined charging and discharging system, so that a simulated environment close to the actual service environment of the measured material is constructed, and the accuracy of a prediction result is improved. In the aging test process, the conductivity of electrolyte in a pipeline between the electrolyte storage tank with the sample and the electric pile is detected. The durability of the measured material in the simulated environment is represented by the conductivity change of the electrolyte, so that the aging test result is accurate, and the operation is simple and convenient.

Description

Technical Field

[0001] This invention relates to the field of aging testing technology, and in particular to a method for evaluating the durability of polymer materials used in flow batteries and an aging test system. Background Technology

[0002] Polymer materials possess advantages such as light weight, good corrosion resistance, good chemical resistance, low transport resistance, low cost, and good processability, leading to their increasingly widespread application in flow batteries. Currently, most components of flow batteries, such as electrode frames, flow guides, bipolar plates, and sealing rubber, are made of polymer materials. Due to prolonged exposure to high temperatures and immersion in the electrolyte, electrolyte molecules gradually permeate into the polymer components. Furthermore, with increasing temperature and electric field, the permeation rate of organic molecules from the electrolyte into the polymer material accelerates significantly, affecting the mechanical properties of the polymer and even damaging its molecular structure. This can lead to leakage and current leakage in the flow battery stack due to polymer material failure. It is also worth noting that additives in the polymer materials can gradually permeate into the electrolyte during service due to rising temperatures, affecting the redox reaction of the battery electrolyte and thus impacting charge-discharge performance and energy efficiency, ultimately reducing battery performance and lifespan.

[0003] Currently, durability studies on polymer materials mainly employ accelerated aging testing methods. Existing accelerated aging testing methods for polymer materials generally only simulate the superposition of two or three environmental factors (such as temperature and electrolyte environment), and cannot comprehensively simulate the material's service environment. They cannot reflect the combined aging effects of multiple factors such as operating temperature, electrolyte environment, and electric field encountered by polymer materials during service in flow batteries. Consequently, the durability obtained in these studies has little correlation with the durability of polymer materials during actual service in flow batteries. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for evaluating the durability of polymer materials for flow batteries and an aging test system.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for evaluating the durability of polymer materials used in flow batteries, comprising the following steps:

[0007] 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.

[0008] The aging test includes the following steps:

[0009] The sample is placed in the electrolyte storage tank, and the sample is submerged in the electrolyte. The temperature of the electrolyte in the electrolyte storage tank is set to the corresponding aging temperature. The flow battery is operated according to the predetermined charge and discharge regime. 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, so as to obtain data on the change of conductivity with the number of charge and discharge cycles of the flow battery at different aging temperatures.

[0010] 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.

[0011] 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.

[0012] Preferably, step S2 includes:

[0013] 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.

[0014] 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.

[0015] 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.

[0016] In a further preferred embodiment, step S21 involves fitting the 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.

[0017] In a further preferred embodiment, the service life prediction model in step S23 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.

[0018] Preferably, in step S1, the aging test is terminated when the conductivity of the electrolyte is monitored to be ≤ a preset conductivity threshold.

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

[0020] Preferably, 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.

[0021] In this application, the temperature is a thermodynamic temperature, and the unit is Kelvin (abbreviated as "K").

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

[0023] Preferably, the charge-discharge regime includes any one of constant current charge-discharge, constant voltage charge-discharge, constant power charge-discharge, and constant resistance charge-discharge.

[0024] Preferably, 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.

[0025] The polypropylene glass fiber reinforced composite material can be a composite material in which 5-40% glass fiber is added to polypropylene resin.

[0026] Secondly, the present invention provides an aging test system for polymer materials used in flow batteries, comprising a flow battery, the flow battery including a stack, a positive electrode side electrolyte tank, a conductivity sensor, a positive electrode side circulation pump, a negative electrode side electrolyte tank, and a negative electrode side circulation pump. The positive electrode side electrolyte tank is used to hold positive electrode electrolyte, and the negative electrode side electrolyte tank is used to hold negative electrode electrolyte. The positive electrode electrolyte outlet of the stack is connected to the inlet of the positive electrode side electrolyte tank via a pipeline. The outlet of the positive electrode side electrolyte storage tank is connected to the positive electrode side circulation pump through a pipeline, and the positive electrode side circulation pump is connected to the positive electrode electrolyte inlet of the fuel cell stack through a pipeline. The positive electrode side electrolyte storage tank is equipped with a temperature control device. The negative electrode electrolyte outlet of the fuel cell stack is connected to the inlet of the negative electrode side electrolyte storage tank through a pipeline, and the outlet of the negative electrode side electrolyte storage tank is connected to the negative electrode side circulation pump through a pipeline. The negative electrode side circulation pump is connected to the negative electrode electrolyte inlet of the fuel cell stack.

[0027] 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.

[0028] Preferably, the aging test system for polymer materials used in flow batteries further includes a bracket, a base, and a support plate, wherein the base is provided with a groove, the support plate is provided with a slot, and the base and the support plate are connected by a support rod.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This invention uses a flow battery to conduct aging tests on the tested material. During the aging test, the tested material is immersed in the electrolyte in an electrolyte storage tank, and the flow battery is charged and discharged in cycles to construct a simulated environment that closely resembles the actual service environment of the tested material, thereby improving the accuracy of the prediction results.

[0031] The durability evaluation method for polymer materials used in flow batteries described in this invention uses a flow battery to conduct aging tests on samples at a set of samples corresponding to one aging temperature. During the aging test, the conductivity of the electrolyte in the pipeline between the electrolyte storage tank containing the sample and the stack is detected, thereby obtaining data on the change of conductivity with the number of charge-discharge cycles of the flow battery at different aging temperatures. The change in electrolyte conductivity is used to characterize the durability of the tested material in a simulated environment, making the aging test results accurate and the operation simple and convenient. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the flow battery provided by the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of the bracket provided by the present invention;

[0034] Figure 3 This is a schematic diagram of a support with a sample inserted. Detailed Implementation

[0035] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0036] In this invention, all directional indicators (such as up and down) are only used to explain the relative positional relationship and movement of the components in a specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

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

[0038] Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] It is understood that in this invention, the temperature is a thermodynamic temperature, and the unit is K.

[0040] In a first aspect, the present invention provides a method for evaluating the durability of polymer materials used in flow batteries, comprising the following steps:

[0041] 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.

[0042] The aging test includes the following steps:

[0043] The sample is placed in the electrolyte storage tank, and the sample is submerged in the electrolyte. The temperature of the electrolyte in the electrolyte storage tank is set to the corresponding aging temperature. The flow battery is operated according to the predetermined charge and discharge regime. 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, so as to obtain data on the change of conductivity with the number of charge and discharge cycles of the flow battery at different aging temperatures.

[0044] 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.

[0045] 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.

[0046] This invention uses a flow battery to conduct aging tests on the test material. During the aging test, the test material is immersed in the electrolyte in an electrolyte tank, and the flow battery is operated according to a predetermined charge and discharge regime, thereby constructing a simulated environment that is close to the actual service environment of the test material, thus improving the accuracy of the prediction results.

[0047] The durability evaluation method for polymer materials used in flow batteries described in this invention uses a flow battery to conduct aging tests on samples at a set of samples corresponding to one aging temperature. During the aging test, the conductivity of the electrolyte in the pipeline between the electrolyte storage tank containing the sample and the stack is detected, thereby obtaining data on the change of conductivity with the number of charge-discharge cycles of the flow battery at different aging temperatures. The change in electrolyte conductivity is used to characterize the durability of the tested material in a simulated environment, making the aging test results accurate and the operation simple and convenient.

[0048] In one embodiment, step S2 includes:

[0049] 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.

[0050] 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.

[0051] 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.

[0052] Specifically, step S21 is based on 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.

[0053] Specifically, 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.

[0054] This invention constructs a service life prediction model based on data showing the change in conductivity with the number of charge-discharge cycles of a flow battery at different aging temperatures. The service life prediction model is then used to predict the service life of polymer materials used in flow batteries, and the service life prediction results can meet the durability evaluation requirements of polymer materials in the flow battery industry.

[0055] In one embodiment, in step S1, the aging test is terminated when the conductivity of the electrolyte is detected to be ≤ a preset conductivity threshold.

[0056] Specifically, the initial conductivity of the electrolyte before the aging test begins is σ0, and the preset conductivity threshold is σ0. m , σ m / σ0 is 0.70 to 0.99, for example, σ0 / σ m It can 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 consisting of any two sets of values.

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

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

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

[0060] In one embodiment, the charge-discharge regime includes any one of constant current charge-discharge, constant voltage charge-discharge, constant power charge-discharge, and constant resistance charge-discharge.

[0061] In one embodiment, 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.

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

[0063] It is understood that the present invention does not impose any particular limitation on the size of the sample, which can be cut according to actual needs. For example, the sample can be a cuboid with a length of 3 to 20 cm and a width of 3 to 20 cm.

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

[0065] Step S1 involves placing the sample in the electrolyte storage tank, specifically including: inserting the sample into the slot of the bracket, opening the tank lid, placing the bracket with the sample inserted into the electrolyte storage tank, and closing the tank lid.

[0066] The support is made of corrosion-resistant materials, such as titanium.

[0067] Secondly, the present invention provides an aging test system for polymer materials used in flow batteries, comprising a flow battery, the flow battery including a stack, a positive electrode side electrolyte tank, a conductivity sensor, a positive electrode side circulation pump, a negative electrode side electrolyte tank, and a negative electrode side circulation pump. The positive electrode side electrolyte tank is used to hold positive electrode electrolyte, and the negative electrode side electrolyte tank is used to hold negative electrode electrolyte. The positive electrode electrolyte outlet of the stack is connected to the inlet of the positive electrode side electrolyte tank via a pipeline. The outlet of the positive electrode side electrolyte storage tank is connected to the positive electrode side circulation pump through a pipeline, and the positive electrode side circulation pump is connected to the positive electrode electrolyte inlet of the fuel cell stack through a pipeline. The positive electrode side electrolyte storage tank is equipped with a temperature control device. The negative electrode electrolyte outlet of the fuel cell stack is connected to the inlet of the negative electrode side electrolyte storage tank through a pipeline, and the outlet of the negative electrode side electrolyte storage tank is connected to the negative electrode side circulation pump through a pipeline. The negative electrode side circulation pump is connected to the negative electrode electrolyte inlet of the fuel cell stack.

[0068] 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.

[0069] In one embodiment, both the outlet of the positive electrode side electrolyte storage tank and the outlet of the negative electrode side electrolyte storage tank are equipped with filters.

[0070] In one embodiment, the aging test system for polymer materials used in flow batteries further includes a bracket, a base, and a support plate. The base has a groove, and the support plate has a slot. The base and support plate are connected by a support rod. In use, the sample is fixed by inserting it into the groove and slot.

[0071] The present invention provides the following embodiments to facilitate understanding of the invention. These embodiments are provided not to limit the scope of the claims.

[0072] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0073] Example 1

[0074] This embodiment provides a method for evaluating the durability of polymer materials used in flow batteries, including the following steps:

[0075] S1. Using the PP glass fiber reinforced composite material provided by Company A as the test material, the test material was cut into several blocks with an area of ​​10cm*20cm as samples. The samples were divided into three groups, with each group of samples corresponding to an aging temperature. Three flow batteries of the same model were used to conduct aging tests on the samples respectively. The aging temperatures corresponding to the three groups of samples were 313.15K, 333.15K and 343.15K respectively.

[0076] The aging test includes the following steps:

[0077] Prepare a flow battery and a support structure. The flow battery is a vanadium redox flow battery, and its structure is as follows: Figure 1 As shown, the flow battery includes a stack 1, a positive electrode side electrolyte tank 2, a conductivity sensor 3, a positive electrode side circulation pump 4, a negative electrode side electrolyte tank 5, and a negative electrode side circulation pump 6. The positive electrode electrolyte outlet of the stack 1 is connected to the inlet of the positive electrode side electrolyte tank 2 via a pipeline. The outlet of the positive electrode side electrolyte tank 2 is connected to the positive electrode side circulation pump 4 via a pipeline. The positive electrode side circulation pump 4 is connected to the positive electrode electrolyte inlet of the stack 1 via a pipeline. Tank 2 is equipped with a temperature control device. The negative electrode electrolyte outlet of the fuel cell stack 1 is connected to 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 to the negative electrode side circulation pump 6 through a pipeline. The negative electrode side circulation pump 6 is connected to the negative electrode electrolyte inlet of the fuel cell stack 1. Both the outlet of the positive electrode side electrolyte storage tank 2 and the outlet of the negative electrode side electrolyte storage tank 5 are equipped with filters to prevent fragments generated by sample aging and breakage during the aging test from entering the fuel cell stack 1.

[0078] A 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 circulation pump 4;

[0079] The structure of the support is as follows Figure 2 As shown, the bracket 7 includes a base 71 and a support plate 72. The base 71 is provided with a groove 75, and the support plate 72 is provided with a slot 74. The base 71 and the support plate 72 are connected by a support rod 73.

[0080] Insert the sample into the slot 74 and recess 75 of the holder (the holder with the sample inserted is as follows). Figure 3 As shown, Figure 3 In the middle, 8 represents the sample), then open the lid 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 lid;

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

[0082] The temperature of the electrolyte in the positive electrode side electrolyte storage tank 2 is set to the corresponding aging temperature, and the flow battery is subjected to charge-discharge cycles (the flow rate of both the positive and negative electrode electrolytes is 50 ml / min, and the current density is 200 mA / cm²). -2 Initiate charging. Stop charging once the voltage reaches 1.55V, then proceed with charging at 200mA / cm. -2 Discharge is performed, and the discharge ends when the voltage becomes 1.0V. The positive side circulation pump 3 and the negative side circulation pump 6 are started to make the flow rate of the negative electrolyte in the system the same as that of the positive electrolyte. The conductivity of the electrolyte in the pipeline connected to the outlet of the positive side electrolyte storage tank 2 is monitored by a conductivity sensor.

[0083] When the electrolyte conductivity is monitored to be ≤ preset conductivity threshold, the aging test is terminated, thereby obtaining data on the conductivity variation 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 Satisfy: σ m =0.75σ0, where σ0 is the initial conductivity of the electrolyte in the positive electrode side electrolyte 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 in Table 1 is 0).

[0084] Table 1

[0085]

[0086]

[0087] Note: " / " in Table 1 indicates that the aging test at the corresponding temperature was not completed 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. According to the fitting formula y=a1+a2x+a3x 2 Polynomial fitting was performed on the conductivity data of flow battery charge-discharge cycle number at different aging temperatures to obtain the relationship between conductivity and flow battery charge-discharge cycle number at different aging temperatures (as shown in Table 2 below).

[0089] The fitting formula is y = a1 + a2x + a3x 2 In the diagram, 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.

[0090] Based on the relationship between conductivity and the number of charge-discharge cycles of a flow battery at different aging temperatures, the number of charge-discharge cycles of the flow battery corresponding to a preset conductivity threshold is calculated. The calculated number of charge-discharge cycles is then used as the service life of the tested material at the corresponding temperature, thus obtaining data on the service life of the tested material as a function of temperature; that is, y = σ m Substituting the relationship between conductivity and the number of charge-discharge cycles of the flow battery at different aging temperatures, the following results were obtained, as shown in Table 2.

[0091] Table 2

[0092]

[0093]

[0094] Based on the data of the service life of the tested material as a function of temperature, a linear fit was performed on lnt and 1 / T to obtain the service life prediction model: lnt = 556.43 / T + 6.9617, with a correlation coefficient R. 2 It is 0.9953;

[0095] 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.

[0096] In this embodiment, the predicted service life of the tested material under the conditions of 293.15K and flow battery operation is: lnt=556.43 / 293.15+6.9617≈8.86, t≈e 8.86 ≈7044 cycles, meaning the tested material can sustain 7044 charge-discharge cycles for a flow battery at a temperature of 293.15K.

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

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. Use the service life prediction model to predict the service life of polymer materials for flow batteries and obtain the service life prediction results. 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.

2. The durability evaluation method for polymer materials used in flow batteries as described in claim 1, 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.

3. The durability evaluation method for polymer materials used in flow batteries as described in claim 1, 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.

4. 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.

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 temperature of each group of samples is greater than the actual operating temperature of the flow battery.

6. 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.

7. 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.

8. 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.

9. The durability evaluation method for polymer materials used in flow batteries as described in claim 1, characterized in that, The aging test is conducted using an aging test system for polymer materials used in flow batteries. This system includes a flow battery, which comprises a stack, a positive electrode-side electrolyte tank, a conductivity sensor, a positive electrode-side circulation pump, a negative electrode-side electrolyte tank, and a negative electrode-side circulation pump. The positive electrode-side electrolyte tank holds the positive electrode electrolyte, and the negative electrode-side electrolyte tank holds the negative electrode electrolyte. The positive electrode electrolyte outlet of the stack is connected to the inlet of the positive electrode-side electrolyte tank. The outlet of the positive electrode side electrolyte storage tank is connected to the positive electrode side circulation pump via a pipeline, and the positive electrode side circulation pump is connected to the positive electrode electrolyte inlet of the fuel cell stack via a pipeline. The positive electrode side electrolyte storage tank is equipped with a temperature control device. The outlet of the negative electrode electrolyte of the fuel cell stack is connected to the inlet of the negative electrode side electrolyte storage tank via a pipeline, and the outlet of the negative electrode side electrolyte storage tank is connected to the negative electrode side circulation pump via a pipeline. The negative electrode side circulation pump is connected to the negative electrode electrolyte inlet of the fuel cell 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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