A rapid test method for durability of hydrogen fuel cell membrane electrode

Abstract

The application relates to a quick test method for hydrogen fuel cell membrane electrode durability, which is based on real vehicle operation conditions, decomposes operation conditions of main factors affecting hydrogen fuel cell service life, and comprises the following specific steps: decomposing real vehicle operation conditions into single-factor durability conditions; selecting corresponding single-factor durability conditions according to main durability directions of the membrane electrode; activating the hydrogen fuel cell stack after starting the stack, collecting the polarization curve of the operation condition; waiting for the working condition to reach the set working condition point, and starting the durability cycle test; collecting the polarization curve after the operation durability cycle condition is cycled for Nn rounds; stopping the durability cycle test according to the index change of the stack in the durability cycle condition test. The service life is calculated according to the change of the attenuation rate in the operation durability condition. Compared with the prior art, the application can effectively accelerate the selection of the hydrogen fuel cell on the membrane electrode, and save the test cost in the membrane electrode selection work.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen fuel cell durability testing technology, and in particular relates to a rapid testing method for the durability of hydrogen fuel cell membrane electrodes. Background Technology

[0002] The durability of hydrogen fuel cells has always been a core issue that urgently needs to be addressed in the industry and in technological research. Traditional hydrogen fuel cell durability testing usually involves simulating real vehicle operation to establish durability cycle conditions. One cycle of the cycle typically includes start-stop, idling, high load, and variable load conditions. That is, the fuel cell is started up and loaded to the idle point and runs for a certain period of time, then loaded to the high load point multiple times, runs in a steady state at the high load point for a certain period of time, then unloaded to the idle point multiple times, runs for a certain period of time, and then shuts down. This cycle is repeated a certain number of times until the degradation rate at the end of the life is reached, thus completing the durability test.

[0003] The lifespan degradation of hydrogen fuel cells primarily stems from the degradation of the membrane electrode assembly (MEA). Therefore, selecting a durable MEA is crucial for the development of hydrogen fuel cells. Typically, MEA selection involves lengthy testing times, high costs, and a high error rate. Thus, refining durability testing methods is essential.

[0004] Patent CN 110749825 A discloses a method and apparatus for establishing accelerated operating conditions for fuel cell durability testing. This method first collects actual operating data from fuel cell vehicles to construct operating conditions for the fuel cell system. Then, for different operating conditions, it decomposes the fuel cell operating conditions into single-factor operating conditions, calculates the voltage decay rate of the fuel cell under different single-factor operating conditions, obtains the influence weights of the single factors corresponding to different fuel cell system operating conditions, and establishes a mathematical model for battery voltage decay. Next, based on the established mathematical model for battery voltage decay, a fuel cell stack model is established and corrected. Based on the correction results, an accelerated operating condition for the fuel cell is established. This invention mainly establishes an accelerated operating condition suitable for fuel cell durability testing under specific real-vehicle operating conditions. The establishment of this accelerated operating condition involves single-factor operating condition influence weight analysis, mathematical model establishment, and fuel cell stack model correction. However, for hydrogen fuel cell development, horizontal comparison of membrane electrode assembly (MEA) durability is too labor-intensive and not suitable for establishing operating conditions for MEA durability selection.

[0005] Patent CN 110850320 A discloses a method for testing the durability of hydrogen fuel cells. The method includes: coating a catalyst slurry onto a proton exchange membrane, then hot-pressing a self-made diffusion layer onto both sides of the catalyst layer to form a membrane electrode assembly (MEA); assembling the MEA into a hydrogen fuel cell and activating the fuel cell as a single cell; collecting the polarization curves of the MEA before and after open-circuit voltage operation of the hydrogen fuel cell; judging the durability of the hydrogen fuel cell based on the polarization curves, AC impedance spectra, linear sweep voltammetry curves, cross-sectional views of the catalyst layer, and fluoride ion concentration before and after open-circuit voltage operation; and analyzing the degradation mechanism of the corresponding MEA by collecting relevant experimental data to calculate the durability, i.e., the lifespan, of the hydrogen fuel cell. This invention's lifespan assessment method uses durability as a factor, which integrates factors such as polarization performance degradation, increased permeability density, increased AC impedance fitting value, catalyst layer cross-section, and increased fluoride ion concentration. However, this method is not intuitive enough for directly estimating the stack's lifespan. In the development of hydrogen fuel cells, comparing the durability of membrane electrode assemblies horizontally is too labor-intensive and not suitable for establishing the selection conditions for membrane electrode durability. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology by providing a rapid testing method for the durability of hydrogen fuel cell membrane electrode assemblies (MEAs). This invention focuses on the causes of individual factors affecting durability and simplifies the breakdown of durability cycle conditions. This can greatly shorten the durability testing time during the MEA selection stage, quickly compare the durability differences of different MEA models, and summarize the degradation law of MEAs by calculating the decay rate within different durability testing time periods. Durability testing can be completed in advance before the end of the stack life, effectively saving durability testing costs and improving durability testing efficiency.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A rapid testing method for the durability of a hydrogen fuel cell membrane electrode assembly (MEA) is provided. Based on actual vehicle operating conditions, the method identifies the main factors affecting the lifespan of the hydrogen fuel cell. The rapid testing method includes the following steps:

[0009] S1. Decompose the actual vehicle operating conditions into individual durability conditions (large load change, idling operation, high load, start-stop);

[0010] S2. Based on the main durability considerations for the membrane electrode, select the appropriate single-factor durability conditions.

[0011] S3. After starting the fuel cell stack, activate the fuel cell stack and collect the polarization curves under operating conditions.

[0012] S4. Wait for the working conditions to reach the set working point, then begin the endurance cycle test;

[0013] S5. Collect the polarization curve after Nn cycles of the endurance cycle operation;

[0014] S6. Stop the durability cycle test based on the changes in the indicators during the durability cycle test of the fuel cell stack.

[0015] Furthermore, the single-factor durability condition in step S2 is a large variable load durability condition.

[0016] Furthermore, the set operating point in step S4 is the idle operating point.

[0017] Furthermore, the durability cycle test in step S4 includes the following steps:

[0018] S41. Run the load to idle speed condition and collect the corresponding voltage;

[0019] S42. Load to rated operating condition, collect the corresponding voltage, and then reduce the load back to idle condition;

[0020] S43. Consider one cycle of idling operation plus rated operation as a loop, and repeat the cycle.

[0021] Further, in step S6, the attenuation rate is calculated based on the polarization curves of the membrane electrode before and after the fuel cell stack undergoes durability cycling. When the attenuation rate exceeds the durability requirements, the durability cycling test is stopped.

[0022] Furthermore, the attenuation rate is the attenuation rate of polarization performance at the maximum idle speed point and at the rated point before and after the operating durability cycle, i.e.

[0023] λ=(V0-Vt) / V0*100%;

[0024] Where λ is the decay rate, V0 is the performance value before the operating durability cycle, and Vt is the performance value after the operating durability cycle.

[0025] Furthermore, in step S6, based on the change in the decay rate during the durability cycle test of the fuel cell stack, the durability cycle test is stopped when the decay rate shows a certain trend.

[0026] Furthermore, once the degradation rate of the hydrogen fuel cell shows a decreasing trend, the test can still be terminated earlier even if the stack degradation has not reached the life degradation index value.

[0027] Furthermore, the durability of the membrane electrode was compared laterally by using the decay rate before the decay rate showed a regular slowdown to estimate the stack lifetime. The lifetime calculated at this time was less than the actual operating lifetime of the stack.

[0028] Furthermore, based on the equivalent operating time of each durability cycle, the actual vehicle's operating time t per cycle is calculated, and the equivalent actual vehicle operating time tn for Nn cycles is calculated accordingly.

[0029] tn = Nn*t;

[0030] The decay rate is calculated using the principle of linear fitting, that is...

[0031] Vi=β0+β1*ti+εi(i=1,2,…n);

[0032] Where (ti, Vi) represents the real-time performance of the fuel cell stack as Vi when the running time is ti, β0 and β1 are parameters, β0+β1*ti is the component reflecting the statistical relationship line, and εi is the random component reflecting the area around the statistical relationship line, and εi follows a normal distribution.

[0033] Based on the idle and rated voltage values ​​collected within the time period ti, β0 and β1 are statistically analyzed, and the estimated values ​​of β0 and β1 are a and b, respectively. A univariate linear equation is then established:

[0034] V = a + b * t;

[0035] The decay rate b of the voltage over time corresponding to the Nn cycles is calculated.

[0036] Based on actual vehicle operating conditions, the main operating conditions affecting the lifespan of hydrogen fuel cells are identified. By analyzing the changes in the degradation rate during the hydrogen fuel cell's endurance operating conditions, the degradation pattern is summarized, and the degradation situation in subsequent operation is predicted. The lifespan of the hydrogen fuel cell is estimated by the degradation rate of polarization performance before and after the endurance operating conditions. This invention can effectively accelerate the selection of membrane electrode assemblies (MEAs) for hydrogen fuel cells, while saving testing costs in the MEA selection process.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] (1) This invention simplifies the breakdown of durability cycle conditions by focusing on the reasons why individual single factors affect durability. This can greatly shorten the durability test time in the membrane electrode selection stage and quickly compare the durability differences of different types of membrane electrodes.

[0039] (2) By calculating the decay rate within different durability test time periods, this invention can summarize the decay law of the membrane electrode, and can complete the durability test in advance before the end of the stack life, effectively saving durability test costs and improving durability test efficiency. Attached Figure Description

[0040] Figure 1 This is a diagram illustrating the high-load durability cycle operation of a hydrogen fuel cell in an embodiment of the present invention.

[0041] Figure 2 This is a polarization curve obtained during the hydrogen fuel cell durability test in an embodiment of the present invention.

[0042] Figure 3 This is a schematic diagram illustrating the voltage change over time during the hydrogen fuel cell durability test in an embodiment of the present invention.

[0043] Figure 4 This is a graph showing the decay rate variation at different time stages during the hydrogen fuel cell durability test in an embodiment of the present invention. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0045] Example

[0046] Figure 1 This durability cycle test is based on actual vehicle operating conditions and is characterized by its focus on the impact of short-term load transitions from idle to high load (i.e., large load changes) on the durability of hydrogen fuel cells. Specifically, it involves a high-speed load transition to idle, operation, and voltage measurement; then a load transition to rated operating conditions, operation, and voltage measurement; finally, a load reduction back to idle. The load transition rates remain consistent throughout the entire process. One cycle of idle condition + rated operating conditions is considered a single cycle, and this durability cycle is repeated. After repeated cycle testing, the fuel cell lifespan is estimated based on the cycle duration.

[0047] In this example, by rapidly varying the load between idle and rated conditions, an accelerated endurance cycle test is provided for the hydrogen fuel cell stack, which can significantly shorten the endurance test time. On the other hand, the decomposed endurance cycle conditions avoid the impact of the hydrogen-air interface caused by start-stop on durability, which can focus on the membrane electrode's tolerance to idle, rated, and large load variations.

[0048] After performing durability test cycles N1, N2, N3, N4, N5, and N6 according to the fuel cell stack, the membrane electrode assembly was tested before and after the durability cycle conditions. Figure 2 The polarization curve shown indicates that the attenuation rate did not reach the pre-specified attenuation target. And as... Figure 3 As shown, b is calculated based on its decay rate: the equivalent operating time t of each round of the durability cycle is calculated based on the operating time of each cycle, and the equivalent operating time t1 of the N1th round is calculated accordingly.

[0049] t1 = N1 * t;

[0050] The decay rate is determined using the principle of linear fitting, i.e.

[0051] Vi=β0+β1*ti+εi(i=1,2,…n);

[0052] Where (ti, Vi) represents the real-time performance of the fuel cell stack at runtime ti, denoted as Vi; β0 and β1 are parameters, β0 + β1 * ti reflects the components of the statistical relationship line, and εi is the random component reflecting the area around the statistical relationship line, εi following a normal distribution. Based on the idle point and rated point voltage values ​​collected within runtime t1, β0 and β1 are statistically analyzed, and the estimated values ​​of β0 and β1 are a and b, respectively. A univariate linear equation is established:

[0053] V = a + b * t;

[0054] Calculate the voltage decay rates b1, b2, b3, b4, b5, and b6 for the following cycles: N1, N2, N3, N4, N5, and N6.

[0055] By analyzing the decay rate at different time stages, such as Figure 4 As shown, the degradation rate of hydrogen fuel cells exhibits a trend of decreasing rate after time intervals t1+t2+t3+t4. At this point, after the N6th durability cycle, even if the stack degradation has not reached the lifespan degradation index, the test can still be terminated early. The durability of the membrane electrode assembly (MEA) can be compared horizontally using the degradation rate b4 before the degradation rate shows a regular slowdown, to estimate the stack lifespan. The calculated lifespan is less than the actual operational lifespan of the stack. This extreme value algorithm allows for rapid horizontal comparison of the durability differences between different MEA models during the MEA selection phase.

[0056] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A rapid testing method for the durability of a hydrogen fuel cell membrane electrode assembly (MEA), comprising, based on actual vehicle operating conditions, decomposing the operating conditions that primarily affect the lifespan of the hydrogen fuel cell, characterized in that, The rapid testing method includes the following steps: S1. Decompose the actual vehicle operating conditions into individual durability operating conditions; S2. Based on the main durability considerations for the membrane electrode, select the appropriate single-factor durability conditions. S3. After starting the fuel cell stack, activate the fuel cell stack and collect the polarization curves under operating conditions. S4. Wait for the working conditions to reach the set working point, then begin the endurance cycle test; Durability cycle testing includes the following steps: S41. Run the load to idle speed condition and collect the corresponding voltage; S42. Load to rated operating condition, collect the corresponding voltage, and then reduce the load back to idle condition; S43. Consider one cycle of idling condition + rated condition as one cycle, and repeat the cycle; S5. Collect the polarization curve after Nn cycles of the endurance cycle condition; S6. Stop the durability cycle test based on the changes in the indicators during the durability cycle test of the fuel cell stack. Based on the polarization curves of the membrane electrode before and after the fuel cell stack undergoes durability cycling, the attenuation rate is calculated. When the attenuation rate exceeds the durability requirements, the durability cycling test is stopped. Alternatively, based on the decay rate changes during the durability cycle test of the fuel cell stack, the durability cycle test is stopped once the decay rate shows a certain trend.

2. The rapid testing method for the durability of a hydrogen fuel cell membrane electrode according to claim 1, characterized in that, The single-factor durability condition in step S2 is the large variable load durability condition.

3. The rapid testing method for the durability of a hydrogen fuel cell membrane electrode according to claim 1, characterized in that, The set operating point in step S4 is the idle operating point.

4. The rapid testing method for the durability of a hydrogen fuel cell membrane electrode according to claim 1, characterized in that, The aforementioned attenuation rate is the attenuation rate of polarization performance at the maximum idle speed point and at the rated point before and after the operating durability cycle. λ=(V0-Vt) / V0*100%; Where λ is the decay rate, V0 is the performance value before the operating durability cycle, and Vt is the performance value after the operating durability cycle.

5. A rapid testing method for the durability of a hydrogen fuel cell membrane electrode according to claim 1, characterized in that, The test was terminated early after the hydrogen fuel cell degradation rate showed a decreasing trend.

6. A rapid testing method for the durability of a hydrogen fuel cell membrane electrode according to claim 5, characterized in that, The durability of the membrane electrode was compared laterally by estimating the stack lifetime using the decay rate before the decay rate showed a regular slowdown.

7. The rapid testing method for the durability of a hydrogen fuel cell membrane electrode according to claim 1, characterized in that, Based on the equivalent operating time of each durability cycle, the actual vehicle's operating time t per cycle is calculated, and the equivalent actual vehicle operating time tn for Nn cycles is calculated accordingly. tn = Nn * t; The decay rate is calculated using the principle of linear fitting, that is... Vi=β0+β1*ti+εi(i=1,2,…n); Where (ti, Vi) represents the real-time performance of the fuel cell stack as Vi when the running time is ti, β0 and β1 are parameters, β0+β1*ti is the component reflecting the statistical relationship line, and εi is the random component reflecting the area around the statistical relationship line, and εi follows a normal distribution. Based on the idle and rated voltage values ​​collected within the time period ti, β0 and β1 are statistically analyzed, and the estimated values ​​of β0 and β1 are a and b, respectively. A univariate linear equation is then established: V = a + b * t; The decay rate b of the voltage over time corresponding to the Nn cycles is calculated.

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