Rapid activation and performance evaluation method for fuel cell stack

Abstract

The invention relates to the technical field of fuel cells, in particular to a rapid activation and performance evaluation method for a fuel cell stack, which is suitable for manufacturing and testing stages of proton exchange membrane fuel cells.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a method for rapid activation and performance evaluation of a fuel cell stack, which is applicable to the manufacturing and testing stages of proton exchange membrane fuel cells. Background Art

[0002] The proton exchange membrane fuel cell (PEMFC) is an efficient and environmentally friendly energy conversion device. Its core principle is to directly generate electricity and water through the electrochemical reaction of hydrogen and oxygen. It is regarded as one of the important technologies in the hydrogen energy economy.

[0003] Traditional activation methods are time-consuming, inefficient, and unable to simultaneously assess performance indicators such as internal water management and catalyst layer attenuation within the fuel cell stack. For example, analysis of the content of the publication (announcement) number CN113594503B, published on January 4, 2022, titled "A Rapid Activation Method for a Fuel Cell Stack," reveals the following issues: 1. Only constant current method is used (no gradient cycle); 2. Constant loading rate 0.08A / cm 2 / s; 3. Maintain constant current for 10 minutes; 4. Fixed 3 cycles; 5. Voltage difference <30mV, single condition; 6. No real-time monitoring, only the final voltage is recorded; 7. Unified testing pressure ≤180kPa; 8. Unified dew point 55℃ (60s); 9. There is no efficiency coefficient, only the voltage recovery rate is recorded.

[0004] For example, the publication (announcement) number is CN116259793A, and the publication (announcement) date is 2023-06-13. An analysis of the content of the document titled “A method for rapid activation of a fuel cell stack” reveals the following issues: 1. Simplified gradient cycle (only 2 cycles); 2. Loading rate 0.12A / cm 2 / s (single rate, no load reduction phase); 3. Peak current is maintained for 3 minutes (no stage adjustment); 4. Fixed 4 cycles (no initial activation degree correlation); 5. Time threshold (total activation time ≤ 2h); 6. Only monitor temperature fluctuations (threshold ±5°C); 7. Anode / cathode ≤ 250kPa (no coolant test); 8. Anode humidification only (dew point 50°C, no cathode treatment); 9. Use power density growth rate (% / min).

[0005] In view of this, research and improvement are carried out on the existing problems, and a method for rapid activation and performance evaluation of a fuel cell stack is provided, aiming to solve the problems in the existing technology through this technology, improve similar situations that occur in the existing technology through this technical solution, and improve the practical value. Summary of the Invention

[0006] The object of the present invention is to provide a method for rapid activation and performance evaluation of a fuel cell stack to solve the problems and deficiencies raised in the above-mentioned background technology.

[0007] To achieve the above objectives, the present invention provides a method for rapid activation and performance evaluation of a fuel cell stack, which is achieved by the following specific technical means: As a further optimization of the technical solution, the present invention provides a method for rapid activation and performance evaluation of a fuel cell stack, comprising the following steps: (a) Airtightness test phase: Nitrogen or hydrogen is introduced into the anode chamber of the fuel cell stack to a pressure of ≤200 kPa, and nitrogen is introduced into the cathode chamber and coolant chamber to a pressure of ≤150 kPa. After maintaining the pressure for 10 minutes, the pressure drop in the three chambers is tested to be ≤5 kPa. (b) Humidification pretreatment stage: adjust the coolant temperature to 60-80°C, pass nitrogen with a dew point of ≥65°C to the cathode for 30 seconds, and then pass hydrogen with a dew point of ≥60°C to the anode for 1 minute; (c) Dynamic load activation phase: A gradient cycle consisting of the following substeps is executed: (c1) When the cell voltage is ≥0.9V, the current is 0.10-0.15A / cm 2 / s rate increases to 0.6A / cm 2 Rated current point, maintain for 5 minutes; (c2) at 0.15A / cm 2 / s rate increases to 0.8-1.0A / cm 2 Peak current point, maintained for 2 minutes; (c3) at 0.18A / cm 2 / s rate to reduce the load to 0.1A / cm 2 Idle current point; (d) Activation verification stage: Cut off the cathode air supply and use a small current to deplete the air until the average cell voltage is ≤10mV and maintain for 30s; (e) Repeat steps (b)-(d) until the activation termination condition is met.

[0008] As a further optimization of the technical solution, the present invention provides a method for rapid activation and performance evaluation of a fuel cell stack, wherein the gradient cycle is performed 3-5 times, and the peak current of adjacent cycles increases by 0.1A / cm As a further optimization of the technical solution, the present invention provides a method for rapid activation and performance evaluation of a fuel cell stack, wherein the activation termination condition is a composite condition: Activation efficiency coefficient K=ΔV / (t·I) ≥0.15mV·cm 2 / (min·A·℃); The voltage difference between adjacent cycle rated current points is less than 50mV; Open circuit voltage fluctuation range <30mV; If any two conditions are met, activation is considered complete.

[0009] As a further optimization of the technical solution, the present invention provides a method for rapid activation and performance evaluation of a fuel cell stack, wherein the dynamic load activation stage includes real-time monitoring of: If the ohmic impedance increase is greater than 15% at rated current, the holding time will be extended by 2 minutes; If the voltage decay rate at the peak current point is greater than 5mV / s, the current cycle is terminated prematurely.

[0010] Due to the application of the above technical solution, the present invention has the following advantages over the prior art: 1. The technical solution of the present invention adopts dynamic gradient cycle plus composite termination conditions to improve the activation efficiency, which is specifically manifested in 3-5 dynamic gradient cycles with an average of 45-70 minutes, through multi-stage current gradient cycle, such as 0.6A / cm 2. The present invention achieves precise control through chamber pressure detection, differentiated humidification, and real-time monitoring intervention. Pressure thresholds are set for the anode, cathode, and coolant respectively, such as the anode ≤200kPa, compared with the existing technology that adopts a unified threshold of ≤180kPa, effectively avoiding damage to the membrane electrode caused by overpressure; at the same time, the pretreatment combination of cathode dew point ≥65℃ and anode dew point ≥60℃, compared with the existing technology that only treats the anode dew point of 50℃, significantly optimizes water management efficiency and reduces "dry burning" or "flooding" during the activation process.

[0011] 3. The present invention proposes an activation efficiency coefficient K, which integrates voltage, time, current and temperature parameters, improves the single indicator in the existing technology, and proposes a multi-parameter evaluation model K=ΔV / (t·I) that integrates voltage change (ΔV), time (t), current (I) and temperature. Compared with the existing technology that only uses power density growth rate or voltage recovery rate, the indicators of the benchmark patent are more in line with actual application needs; by monitoring the ohmic impedance increase threshold of 15% and the voltage decay rate threshold of 5mV / s, the activation process is dynamically adjusted to reduce life loss caused by excessive activation. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0013] The present invention provides a specific technical implementation scheme of a method for rapid activation and performance evaluation of a fuel cell stack: Example 1, standard activation process: 1. Air tightness test (1) Install the fuel cell stack on the airtightness test bench and close all outlet pipes; (2) Hydrogen is introduced into the anode chamber to a pressure of 180 kPa, and nitrogen is introduced into the cathode chamber and the cooling liquid chamber to a pressure of 140 kPa; (3) After maintaining the pressure for 10 minutes, the following test results were obtained: the pressure drop in the anode chamber was 3.2 kPa, the pressure drop in the cathode chamber was 4.1 kPa, and the pressure drop in the coolant chamber was 2.8 kPa, which met the requirement of ≤5 kPa.

[0014] 2. Humidification pretreatment (1) Set the coolant temperature to 70°C and wait until the outlet temperature stabilizes; (2) Nitrogen with a dew point of 68°C is introduced into the cathode for 30 seconds; (3) Introduce hydrogen with a dew point of 62°C into the anode for 1 minute.

[0015] 3. Dynamic load activation (1) Switch the cathode gas supply to air and monitor the cell voltage rising to 0.92V; (2) At 0.12A / cm 2 / s rate increases to 0.6A / cm 2 , maintain for 5 minutes (during which the ohmic impedance increases by 12%); (3) At 0.15A / cm 2 / s to 0.9A / cm 2 Peak point, maintained for 2 minutes (voltage decay rate 3.8mV / s); (4) At 0.18A / cm 2 / s down to 0.1A / cm 2 Idle point.

[0016] 4. Performance Verification (1) After cutting off the air supply, use a small current of 5A to deplete the air until the cell voltage reaches 8mV and maintain this for 30s; (2) After repeating the cycle 3 times, the following results were obtained: Activation efficiency coefficient K = 0.17mV·cm 2 / (min·A·℃) The voltage difference between adjacent cycles is 42mV Open circuit voltage fluctuation 25mV The activation is determined to be complete.

[0017] Specifically, during the dynamic load phase, a cycle is detected: When the ohmic impedance of the flow point increases by 17%, the holding time is automatically extended to 7 minutes; When the peak current point voltage decay rate is 6.2mV / s, the cycle is terminated early, and the system automatically adds one supplementary cycle to meet the termination condition.

[0018] It should be noted that: 1. Cycle design: through 0.6→0.9→0.1A / cm 2 Three-stage load change to achieve: Rated current point (5min): Promotes hydration balance of proton exchange membrane; Peak current point (2 min): accelerates the stripping of the oxide layer on the catalyst surface; Idle current point: Restore the drainage capacity of the gas diffusion layer.

[0019] 2. Activation efficiency coefficient algorithm: K = ΔV / (t·I) Where ΔV is the voltage difference at the rated current point before and after activation, t is the total activation time, and I is the average current density. This coefficient comprehensively reflects the relationship between activation speed and quality.

[0020] In summary, the method for rapid activation and performance evaluation of a fuel cell stack adopts a gradient cyclic load strategy of 0.6A / cm2, which is different from the prior art which adopts a static constant current or a fixed number of cycles. At the same time, a new activation efficiency coefficient K (K=ΔV / (t·I)) is added as a composite termination condition, which is different from the single voltage or time threshold in the existing technology.

[0021] Through dynamic gradient activation, multi-dimensional evaluation system and real-time control mechanism, the problems of low efficiency and poor adaptability in traditional methods have been solved, and the commercial application potential of fuel cell stacks has been enhanced.

[0022] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for rapid activation and performance evaluation of a fuel cell stack, characterized in that The following steps are involved: (a) Airtightness test phase: Nitrogen or hydrogen is introduced into the anode chamber of the fuel cell stack to a pressure of ≤200 kPa, and nitrogen is introduced into the cathode chamber and coolant chamber to a pressure of ≤150 kPa. After maintaining the pressure for 10 minutes, the pressure drop in the three chambers is tested to be ≤5 kPa. (b) Humidification pretreatment stage: adjust the coolant temperature to 60-80°C, pass nitrogen with a dew point of ≥65°C to the cathode for 30 seconds, and then pass hydrogen with a dew point of ≥60°C to the anode for 1 minute; (c) Dynamic load activation phase: A gradient cycle consisting of the following substeps is executed: (c1) When the cell voltage is ≥0.9V, the current is 0.10-0.15 A / (cm 2 ·s) rate is increased to 0.6A / cm 2 Rated current point, maintain for 5 minutes; (c2) at 0.15A / cm 2 / s rate increases to 0.8-1.0A / cm 2 Peak current point, maintained for 2 minutes; (c3) at 0.18A / cm 2 / s rate to reduce the load to 0.1A / cm 2 Idle current point; (d) Activation verification stage: Cut off the cathode air supply and use a small current to deplete the air until the average cell voltage is ≤10mV and maintain for 30s; (e) Repeat steps (b)-(d) until the activation termination condition is met.

2. A method for rapid activation and performance evaluation of a fuel cell stack according to claim 1, characterized in that: The gradient cycle was performed 3-5 times, and the peak current of adjacent cycles increased by 0.1 A / cm 2 , when the initial activation degree is less than 70%, 5 cycles are performed, and when the initial activation degree is ≥70%, 3 cycles are performed.

3. A method for rapid activation and performance evaluation of a fuel cell stack according to claim 1, characterized in that: The activation termination condition is a composite condition: Activation efficiency coefficient K=ΔV / (t·I) ≥0.15mV·cm 2 / (min·A·℃); The voltage difference between adjacent cycle rated current points is less than 50mV; Open circuit voltage fluctuation range <30mV; If any two conditions are met, activation is considered complete.

4. A method for rapid activation and performance evaluation of a fuel cell stack according to claim 1, characterized in that: The dynamic load activation phase includes real-time monitoring of: If the ohmic impedance increase is greater than 15% at rated current, the holding time will be extended by 2 minutes; If the voltage decay rate at the peak current point is greater than 5mV / s, the current cycle is terminated prematurely.