KR20230138824A - Fuel Cell Durability Evaluation Method - Google Patents

Abstract

According to one embodiment of the present disclosure, a method for evaluating the durability of an air-cooled polymer fuel cell stack is provided. The method comprises: (a) a preparation step of confirming that the impedance of the fuel cell stack is maintained constant while driving a constant current or varying a load; (b) an information acquisition step of evaluating the durability of the fuel cell stack prepared for durability evaluation and including a start-up (SU) step (b1) in which hydrogen is supplied to the fuel cell stack through an anode and an open circuit voltage is generated in the fuel cell stack, a constant current driving step (b2) in which the fuel cell stack is driven so that a preset constant current value is generated in the fuel cell stack, and a shut-down (SD) step (b3) in which the hydrogen inflow through the anode is stopped; (c) a unit cell analysis step of dismantling the fuel cell stack, in which the information acquisition for durability evaluation is completed in the step (b), and evaluating the performance of each unit cell; and (d) a step of evaluating the durability of the fuel cell stack and calculating the lifespan using the information acquired in the step (b).

Description

Fuel Cell Durability Evaluation Method}

This disclosure relates to a fuel cell durability evaluation method, and specifically to a durability evaluation method specialized for air-cooled polymer fuel cell stacks.

The content described in this section simply provides background information for the present disclosure and does not constitute prior art.

A fuel cell is a battery that generates electrical energy by electrochemically reacting fuel and oxidizer. Fuel cells are currently attracting attention as an alternative energy source in many fields due to their high efficiency, ability to use a variety of fuels, and eco-friendly emissions.

Depending on the type of fuel used, fuel cells include phosphoric acid type (PAFC), alkaline type (AFC), polymer electrolyte type (PEMFC), direct methanol type (DMFC), and solid oxide type (SOFC). Among these, polymer electrolyte type (PEMFC; proton exchange membrane fuel cells) batteries use solid polymers at relatively low temperatures and have a high output voltage, so research is being actively conducted for commercialization. PEMFC can be largely used for transportation, vehicles, household and building applications.

In the case of PEMFC for transport, it is common to use a small stack with a power of about 1 kW, so the PEMFC is cooled using air cooling rather than water cooling.

Meanwhile, air-cooled PEMFC has an open cathode structure. Specifically, the cathode is open to the atmosphere, and a fan attached to the cathode side supplies air. However, the air-cooled PEMFC stack cannot be strongly fastened, making perfect sealing from the outside air difficult. Accordingly, air easily flows into the anode, and a hydrogen-air interface is formed at the anode, which increases the cathode potential, which may lead to deterioration of the electrode and electrolyte membrane.

For this reason, the importance of accurate durability evaluation is emerging in the case of air-cooled PEMFC. However, research on air-cooled PEMFC is insufficient, and in particular, there is almost no research on durability evaluation of air-cooled PEMFC.

(Patent Document 1) KR 10-1033888 B1

(Patent Document 2) KR 10-2020-0074541 A

(Patent Document 3) KR 10-2021-0008198 A

Accordingly, the purpose of the present disclosure is to provide a method for objectively evaluating the durability of an air-cooled fuel cell stack.

Additionally, the present disclosure aims to provide a method for quickly evaluating the durability of an air-cooled fuel cell stack by shortening the evaluation time.

Additionally, the present disclosure aims to provide a method for evaluating the degree of deterioration of each part of an air-cooled fuel cell stack.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

According to an embodiment of the present disclosure, a method of evaluating the durability of an air-cooled polymer fuel cell stack includes (a) a preparation step of confirming that the impedance of the fuel cell stack is maintained constant while driving a constant current or changing the load; ; (b) As an information acquisition step for evaluating the durability of the fuel cell stack ready for durability evaluation, (b1) hydrogen begins to be supplied to the fuel cell stack through the anode, and an open circuit voltage is generated in the fuel cell stack. (start-up) stage; (b2) a constant current driving step of driving the fuel cell stack so that a preset constant current value is generated in the fuel cell stack; and (b3) an information acquisition step for durability evaluation, including a SD (shut-down) step in which hydrogen inflow through the anode is stopped; (c) a unit cell analysis step of dismantling the fuel cell stack for which information for durability evaluation has been completed in step (b) and evaluating the performance of each unit cell; and (d) evaluating the durability of the fuel cell stack and calculating its lifespan using the information obtained in step (b).

Also, preferably, step (b1) of the present disclosure is performed for 10 to 50 seconds, and the preset constant current in step (b2) is 100 mA/cm ² to 600 mA/cm ² , Step (b2) is performed for 180 to 420 seconds, and step (b3) includes stopping the inflow of hydrogen into the anode until the output voltage per unit cell of the fuel cell stack is 0.1 V to 0.2 V. do.

In addition, preferably, step (b) of the present disclosure includes (b4) steps (b1) to (b3) as one cycle, and each cycle is repeated multiple times, and the I (current) of the fuel cell stack is adjusted every n cycles. ) - Performance reduction rate calculation step of measuring V (output voltage) and impedance and using this to calculate the performance reduction rate of the fuel cell stack - n is a natural number -; (b5) If it is determined that the rate of performance decline is increasing, repeating each cycle multiple times and measuring the I-V and impedance of the fuel cell stack for each m cycle, where m is a natural number less than or equal to n; and (b6) terminating the information acquisition step for durability evaluation when the output voltage last measured in step (b5) is less than a preset certain ratio compared to the output voltage initially measured in step (b4). Includes.

Also, preferably, in step (b4) of the present disclosure, n is 100, in step (b5), m is 30 to 50, and in step (b6), the preset constant ratio is 30. % to 50%.

Also, preferably, step (c) of the present disclosure includes: (c1) dividing the fuel cell stack into 2 to 3 unit cells; (c2) repeating steps (b1) to (b3) and measuring I-V, impedance, cyclic voltammetry (CV), and linear sweep voltammetry (LSV) for each unit cell of the divided fuel cell stack; (c3) evaluating the performance of each unit cell using the measured I-V, impedance, CV, and LSV for each unit cell using a preset method; (c4) confirming the thickness of the electrode and the thickness of the film using the cross-sections of the unit cells of the fuel cell stack divided into equal parts; and (c5) evaluating the degree of deterioration for each unit cell by comparing the thickness of the electrode and the thickness of the film for each confirmed unit cell.

Also, preferably, in step (c1) of the present disclosure, the fuel cell stack is divided into two parts: a hydrogen inflow side unit cell and a hydrogen outflow side unit cell, or the fuel cell stack is divided into a hydrogen inflow side unit cell and a central unit cell. and the unit cell on the hydrogen outflow side are divided into three parts.

Also, preferably, according to another embodiment of the present disclosure, step (d) is performed by comparing (d1) the total number of cycles repeated from steps (b4) to (b5) with a preset reference number, A durability evaluation step to evaluate the durability of the fuel cell stack; and (d2) calculating the lifespan of the fuel cell stack by multiplying the total number of cycles repeated from steps (b4) to (b5) by the average operating time of the device in which the fuel cell stack is used.

As described above, according to this embodiment, the durability evaluation method of the air-cooled fuel cell stack is effective in objectively evaluating the durability of the fuel cell stack by applying the same method regardless of the type of air-cooled fuel cell.

In addition, the durability evaluation method of an air-cooled fuel cell stack according to the present disclosure has the effect of shortening the overall durability evaluation method time by adjusting the time of the constant current driving step.

In addition, the method for evaluating the durability of an air-cooled fuel cell stack according to the present disclosure has the effect of being able to confirm deterioration in each part of the fuel cell stack by including an analysis step for each unit cell, thereby promoting an efficient management method.

Figure 1 shows an apparatus for evaluating a fuel cell stack according to an embodiment of the present disclosure.
Figure 2 is a conceptual diagram of a fuel cell stack according to an embodiment of the present disclosure.
Figure 3 is a flowchart of a method for evaluating the durability of a fuel cell stack according to an embodiment of the present disclosure.
Figure 4 shows a specific sequence of preparation steps according to an embodiment of the present disclosure.
Figure 5 is an example of an IV curve in the information acquisition step for durability evaluation according to an embodiment of the present disclosure.
Figure 6 shows a specific sequence of information acquisition steps for durability evaluation according to an embodiment of the present disclosure.
Figure 7 shows a specific sequence of analysis steps for each unit cell according to an embodiment of the present disclosure.
Figure 8 shows a specific sequence of durability evaluation and lifespan calculation steps according to an embodiment of the present disclosure.

Hereinafter, some embodiments of the present disclosure will be described in detail through illustrative drawings. When adding reference signs to components in each drawing, it should be noted that the same components are given the same reference numerals as much as possible even if they are shown in different drawings. Additionally, in describing the present disclosure, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present disclosure, the detailed description will be omitted.

In describing the components of the embodiment according to the present disclosure, symbols such as first, second, i), ii), a), and b) may be used. These codes are only used to distinguish the component from other components, and the nature, sequence, or order of the component is not limited by the code. In the specification, when a part is said to 'include' or 'have' a certain element, this means that it does not exclude other elements, but may further include other elements, unless explicitly stated to the contrary. .

In the present disclosure, each flowchart is shown as being performed in a time-series order, but is not necessarily limited thereto. For example, it should be noted that multiple steps according to each flowchart may be performed simultaneously.

Fuel cell stack evaluation device

Figure 1 shows an apparatus for evaluating a fuel cell stack according to an embodiment of the present disclosure. Figure 2 is a conceptual diagram of a fuel cell stack according to an embodiment of the present disclosure.

Referring to FIG. 1, an apparatus for evaluating a fuel cell stack 1 according to an embodiment of the present disclosure includes a fuel cell stack 1, a solenoid valve 2, a power meter 3, and a load 4. Includes.

The fuel cell stack 1 is composed of a plurality of cells, and in this disclosure, it is described assuming that it is composed of 13 cells (see FIG. 2). One cell (single cell) includes an anode, a cathode, and a membrane disposed between the anode and the cathode. A plurality of cells are arranged in series to form one fuel cell stack (1).

Meanwhile, as hydrogen flows into the anode, current is generated by oxidation/reduction reactions inside the cell. Due to the generated current, a fan attached to the fuel cell stack 1 is driven, and as a result, external air flows into the cathode and heat generated in the fuel cell stack 1 can be dissipated.

The solenoid valve 2 is disposed on the flow pipe through which hydrogen flows and is configured to control the opening and closing of the flow pipe.

The power meter 3 is disposed on a conductor connecting the anode and the cathode and is configured to measure the power generated by the fuel cell stack 1.

The load 4 is disposed on a conductor connecting the anode and the cathode and is configured to form a load on the conductor. At this time, the load 4 may preferably be a variable resistor.

Below, a method for evaluating the durability of the fuel cell stack 1 using a fuel cell stack evaluation device according to an embodiment of the present disclosure will be described.

Evaluation method of fuel cell stack

Figure 3 is a flowchart of a method for evaluating the durability of a fuel cell stack according to an embodiment of the present disclosure.

Referring to FIG. 3, the durability evaluation method of the fuel cell stack 1 according to the present disclosure includes a preparation step (S300), an information acquisition step for durability evaluation (S310), an analysis step for each unit cell (S320), and durability evaluation. and all or part of the life calculation step (S330).

In the preparation step (S300), the fuel cell stack 1 is activated. When the fuel cell stack 1 is stored for a long period of time, the membrane dries and the performance may decrease due to oxidation of the catalyst. In the preparation stage, the fuel cell stack 1 is driven to generate a constant current in the fuel cell stack 1 to recover this decrease in performance to some extent and enable accurate durability evaluation. In relation to this, it will be described in detail in FIGS. 4 to 5.

Additionally, in the information acquisition step for durability evaluation (S310), information for evaluating the durability of the fuel cell stack 1 that is ready for durability evaluation through the preparation step (S300) is obtained. Specifically, the information acquisition step for durability evaluation (S310) includes a start-up (SU) step, a constant current driving step, and a shut-down (SD) step. In relation to this, it will be described in detail in FIG. 6.

Additionally, in the analysis step for each unit cell (S320), the fuel cell stack 1, whose durability has been measured in the durability driving step, is divided into two or three equal parts. Through this, there is an advantage of being able to determine the degree of durability reduction and deterioration for each section of the fuel cell stack 1. This has the effect of promoting an efficient management method for the fuel cell stack 1. In relation to this, it will be described in detail in FIG. 7.

Additionally, in the durability evaluation and life calculation step (S330), the relative durability of the fuel cell stack 1 can be confirmed by comparing the durability of the fuel cell stack 1 with a preset standard. Additionally, the lifespan of the fuel cell stack 1 can be known by multiplying the number of cycles and the average cycle time calculated in step S310. In relation to this, it is explained in detail in FIG. 8.

Figure 4 shows a specific sequence of preparation steps according to an embodiment of the present disclosure.

Referring to FIG. 4, the detailed steps of the preparation step (S300) of the present disclosure will be described.

(a1) Drive the fuel cell stack with constant current or It includes the step of varying the load 4 (S400). By driving the fuel cell stack with a constant current, oxidation and reduction reactions proceed inside the cells of the fuel cell stack 1, and as a result, the fuel cell stack 1 can be activated.

Meanwhile, the above-described S400 process is preferably performed under conditions of room temperature and relative humidity of 40% to 80%.

During constant current driving or the process of changing the load 4 (a2), the I-V and impedance of the fuel cell stack 1 are measured (S410).

(a3) The I-V and impedance of the measured fuel cell stack 1 are monitored, and if the impedance is confirmed to maintain a constant value for a preset time, the fuel cell stack 1 is judged to be stabilized, and the preparation step is performed. It ends (S420).

Figure 5 is an example of an I-V curve in the information acquisition step for durability evaluation according to an embodiment of the present disclosure. Figure 6 shows a specific sequence of information acquisition steps for durability evaluation according to an embodiment of the present disclosure.

With reference to FIGS. 5 and 6, the information acquisition step (S310) for durability evaluation of the present disclosure will be described in detail.

Meanwhile, in the graph of FIG. 5, the horizontal axis represents time (seconds), and the vertical axis represents voltage (V). Additionally, the graph in FIG. 5 shows the results of an experiment in which the fuel cell stack 1 consisting of 13 cells in FIG. 2 was driven at 25°C.

The information acquisition step for durability evaluation includes (b1) SU step, (b2) constant current driving step, and (b3) SD step. Hereinafter, steps (b1) to (b3) are defined as one cycle. The voltage and current changes in one cycle are displayed as I-V curves in Figure 5. Below, each step is described in detail.

(b1) Hydrogen begins to be supplied to the fuel cell stack (1) through the anode. Although not specifically shown in FIG. 2, as oxygen is supplied to the fuel cell stack 1, oxidation/reduction reactions occur inside the fuel cell stack 1. Because of this, current flows through the fuel cell stack 1 to the conductor connected to the fuel cell stack 1.

At this time, the fuel cell stack 1 generates an open circuit voltage (OCV) or a voltage as the current flowing in the connected conductor passes through the resistor or the fan (S600).

Step S600, that is, step SU, corresponds to processes ① to ② in the graph of FIG. 5. Referring to FIG. 5, it can be seen that in the SU stage, the voltage generated by the fuel cell stack 1 is constant. The SU stage is the stage in which hydrogen flows into the stack and voltage is formed, and is based on the time when the voltage of the stack stabilizes. According to Figure 5, it can be seen that the SU step lasts for 30 seconds.

(b2) After the SU step, a constant current driving step is performed in which the fuel cell stack 1 is driven so that a preset constant current value is generated in the fuel cell stack 1 (S610).

Step S610, that is, the constant current driving step, corresponds to processes ③ to ④ in the graph of FIG. 5. Referring to FIG. 5, it can be seen that in the constant current driving stage, the voltage generated by the fuel cell stack 1 is within a certain voltage range (about 8V to 10V in this example). Meanwhile, the duration of the constant current driving step is preferably 180 to 420 seconds, and according to FIG. 5, it can be seen that the constant current driving step lasts for 270 seconds. Additionally, the constant current generated is preferably in the current density range of 100 to 600 mA/cm ² .

Meanwhile, in order to shorten the overall time required for the information acquisition step for durability evaluation, it is desirable to select a short time.

(b3) After the constant current driving step, the inflow of hydrogen supplied through the anode is stopped (S620). Hereinafter, this stage is referred to as the SD stage. As the hydrogen supply is stopped in the SD stage, the oxidation/reduction reaction stops, the hydrogen at the anode is consumed, and the voltage decreases. At this time, the SD stage is maintained until the voltage per cell reaches a certain standard. Here, it is preferable that the certain standard is 0.1 V to 0.2 V. The SD stage can be viewed as a stage in which the hydrogen remaining inside the fuel cell stack is consumed, the voltage decreases, and the secondary battery of the system is charged. Therefore, the SD time is based on the time for the voltage of the stack to sufficiently decrease to a certain standard.

(b4) Steps (b1) to (b3) are counted as one cycle, and the I-V and impedance of the fuel cell stack (1) are measured every time a total of n cycles are repeated, and the performance of the fuel cell stack (1) is measured using this. Calculate the reduction speed (S630).

n times is the minimum number of cycle repetitions at which performance deteriorates, which is derived theoretically or experimentally. In the experimental examples according to FIGS. 2 and 5, cycles (b1) to (b3) were repeated a total of 100 times. That is, the I-V and impedance of the fuel cell stack 1 are measured once every 100 cycles.

(b5) If it is determined that the rate of decline in the measurement performance of the fuel cell stack 1 is increasing, the I-V and impedance of the fuel cell stack 1 are measured every time a total of m cycles are repeated (S640). At this time, m corresponds to a natural number smaller than n.

In the experimental examples according to FIGS. 2 and 5, cycles (b1) to (b3) were repeated a total of 30 to 50 times. That is, the I-V and impedance of the fuel cell stack 1 are measured once every 30 to 50 cycles.

As such, the method according to the present disclosure has the effect of being able to consider changes in I-V characteristics due to deterioration of the fuel cell stack 1 through more frequent I-V and impedance measurements in step (b5) than in step (b4).

(b6) If the output voltage of the fuel cell stack 1 measured in step (b5) is measured to be less than or equal to a preset ratio compared to the initial output voltage, the durability evaluation step ends (S650).

Here, the initial output voltage refers to the voltage confirmed at the beginning of measurement in step (b4), preferably the first output voltage. Additionally, the preset ratio is preferably 30% to 50%.

Meanwhile, in the case of measuring the voltage in each cell of the fuel cell stack 1, I-V in the SU stage, constant current drive stage, and SD stage in each cell can be measured, and each cell can be measured from the voltage change in each section. You can see a decrease in the performance of cells.

Figure 7 shows a specific sequence of analysis steps for each unit cell according to an embodiment of the present disclosure.

With reference to FIG. 7, the detailed steps of the analysis step (S320) for each unit cell according to the present disclosure will be described.

(c1) The fuel cell stack 1 is divided into a plurality of unit cells. Specifically, the fuel cell stack 1 is divided into two or three parts and divided into two or three unit cells (S700). At this time, the membrane-electrode assembly (MEA) is divided into equal parts. For example, the fuel cell stack 1 in FIG. 2 is composed of 13 MEAs stacked vertically, and is divided into equal parts parallel to the direction in which the fuel cell stack 1 is stacked.

Meanwhile, when the fuel cell stack 1 is divided into two, it is divided into a hydrogen inflow MEA and a hydrogen outflow MEA. Additionally, when the fuel cell stack 1 is divided into three parts, it is divided into a hydrogen inflow MEA, a central MEA, and a hydrogen outflow MEA.

Preferably, the analysis step for each unit cell is performed under conditions of 40°C to 70°C and relative humidity of 40% to 100%.

(c2) While repeating steps S600 to S620 for each of the separated hydrogen inflow MEA and hydrogen outflow MEA, all or part of the I-V, impedance, CV (cyclic voltammetry), and LSV (linear sweep voltammetry) of each unit cell are measured ( S710).

At this time, preferably, when measuring CV, the electrochemical surface area (ECSA) is measured using a Potentiostat (Solatron, SI 1287). Also, preferably, when measuring LSV, hydrogen crossover current density and short resistance are measured using a potentiostat.

(c3) The performance of each unit cell is evaluated using the measured I-V, impedance, CV, and LSV of each unit cell using a preset method (S720).

For example, in the same test environment, when different V is measured for each unit cell for the same I, the unit cell with a higher V measured may be evaluated as having better performance. Additionally, when different impedances are measured for each unit cell at the same I, the unit cell with a lower impedance measured may be evaluated as having better performance. Additionally, through CV analysis, the deterioration rate on the electrode surface of each unit cell can be determined.

In other words, by measuring I, V, impedance, CV, and LSV for each unit cell, the electrochemical properties, stability, and efficiency of each unit cell can all be confirmed, which has the advantage of enabling more accurate analysis.

(c4) A cross-section of the unit cells of the equally divided fuel cell stack 1 is photographed, and the thickness of the electrode and the thickness of the film are confirmed (S730).

At this time, preferably, the cross section of each unit cell can be confirmed through scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) analysis.

(c5) By checking the electrode and film thickness through cross-sectional analysis of the unit cell, the deterioration of each unit cell can be compared (S740). For example, in the case of the fuel cell stack 1 divided into two, it can be confirmed which part of the hydrogen inflow MEA and the hydrogen outflow MEA deteriorates more quickly.

Specifically, a hydrogen and air boundary layer is formed in the MEA in contact with hydrogen and air in the SU stage and SD stage. For this reason, deterioration of the electrode layer near the MEA of the unit cell, which is easily in contact with air, progresses most quickly. The advantage is that the S730 step allows you to directly check areas that require structural improvement.

Additionally, deterioration can be observed for each unit cell and data regarding this can be collected. By analyzing the measured data, it is possible to identify cases where abnormal deterioration occurs. Here, abnormal deterioration includes cases where deterioration occurs faster than average data, or deterioration actively progresses in unit cells other than the unit cell in which deterioration mainly occurs.

By confirming this abnormal deterioration, the cause can be determined. The durability of the fuel cell stack 1 can be improved by identifying the specific cause of the deterioration and solving it.

Figure 8 shows a specific sequence of durability evaluation and lifespan calculation steps according to an embodiment of the present disclosure.

With reference to FIG. 8, detailed steps of the durability evaluation and lifespan calculation step (S330) according to the present disclosure will be described.

(d1) In the durability evaluation step of the fuel cell stack 1, the total number of cycles repeated in steps S630 to S640, that is, steps (b4) to (b5), and the reference number are compared (S800).

At this time, the standard number of times refers to the number of times obtained through durability evaluation of the fuel cell stack 1 of the same capacity and same purpose. For example, when n is 200 times and the standard number of times is 150 times, the durability of the fuel cell stack 1, which is the subject of durability evaluation, may be evaluated as superior to the durability of the general fuel cell stack 1. Of course, in step S800 of the present disclosure, the duration of one cycle of the fuel cell stack 1, which is the subject of durability evaluation, is the same as the duration of one cycle performed for measurement in the information acquisition step of a general fuel cell.

(d2) In the durability evaluation step of the fuel cell stack 1, the total number of cycles from steps S630 to S640, i.e., steps (b4) to (b5), and steps S600 to S620, i.e., steps (b1) to (b3). The lifespan of the fuel cell stack 1 is calculated by multiplying the average of the time taken up to (S810).

The total number of cycles from steps (b4) to (b5) means the number of times the cycle n times has been repeated multiplied by x times, and the number of cycles m times have been repeated multiplied by y. At this time, n and m are the minimum number of cycle repetitions to measure I-V, impedance, CV, and LSV once. Meanwhile, note that when measuring the electrical characteristics of the fuel cell stack 1 by subdividing it into more stages in addition to n times and m times, the total number of cycles can take into account the minimum number of repetitions for each of these stages. In addition, x times and y times mean the number of times the cycle is repeated n times and the number of times the cycle is repeated m times, respectively. For example, n times may be 100 times, and m times may be 30 times. In this case, measure I-V, impedance, CV, and LSV once every 100 cycles, and if you notice an increasing rate of performance decline, measure I-V, impedance, CV, and LSV once every 30 cycles. will be confirmed. At this time, if the number of times the cycle is repeated 100 times until it is confirmed that the rate of performance decrease is 10, and the number of times the cycle is repeated 30 times until it is confirmed that the rate of performance decrease is 5 times, x is 10, y becomes 5. In this case, the total number of cycles is n·x+m·y, that is, 100·10+30·5=1150. Please note that the above numbers are merely examples to aid understanding, and that the values of n, m, x, and y may vary depending on the specifications of the fuel cell and the experimental environment.

Meanwhile, according to another embodiment of the present disclosure, the average lifespan can be calculated by multiplying the total number of cycles by the average operating time of the device using the fuel cell stack 1, rather than the time required for S600 to S620. For example, when the fuel cell stack 1 is used in an electric vehicle, when the vehicle is normally driven, the time from the time the engine is turned on to the time the engine is turned off can be multiplied by the total number of cycles.

The above description is merely an illustrative explanation of the technical idea of the present embodiment, and those skilled in the art will be able to make various modifications and variations without departing from the essential characteristics of the present embodiment. Accordingly, the present embodiments are not intended to limit the technical idea of the present embodiment, but rather to explain it, and the scope of the technical idea of the present embodiment is not limited by these examples. The scope of protection of this embodiment should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of this embodiment.

1: Fuel cell stack
2: Solenoid valve
3: Power meter
4: load

Claims (7)

As a method for evaluating the durability of an air-cooled polymer fuel cell stack,
(a) a preparation step of confirming that the impedance of the fuel cell stack is maintained constant while driving a constant current or changing the load;
(b) a step of obtaining information for evaluating the durability of the fuel cell stack ready for durability evaluation,
(b1) SU (start-up) step in which hydrogen begins to be supplied to the fuel cell stack through the anode and an open-circuit voltage is generated in the fuel cell stack;
(b2) a constant current driving step of driving the fuel cell stack so that a preset constant current value is generated in the fuel cell stack; and
(b3) SD (shut-down) step in which hydrogen inflow through the anode is stopped
An information acquisition step for durability evaluation including;
(c) a unit cell analysis step of dismantling the fuel cell stack for which information for durability evaluation has been completed in step (b) and evaluating the performance of each unit cell; and
(d) evaluating the durability of the fuel cell stack and calculating its lifespan using the information obtained in step (b) above.
Including,
method.
According to paragraph 1,
Step (b1) is performed for 10 to 50 seconds,
In step (b2), the preset constant current is 100 mA/cm ² to 600 mA/cm ² , and step (b2) is performed for 180 seconds to 420 seconds,
Step (b3) includes stopping the inflow of hydrogen into the anode until the output voltage per unit cell of the fuel cell stack is 0.1 V to 0.2 V,
method.
According to paragraph 2,
In step (b),
(b4) Repeat steps (b1) to (b3) as one cycle and repeat each cycle multiple times, measuring the I (current) - V (output voltage) and impedance of the fuel cell stack for each n cycle, and using these Performance reduction rate calculation step for calculating the performance reduction rate of the fuel cell stack - n is a natural number -;
(b5) if it is determined that the rate of performance decline is increasing, repeating each cycle multiple times and measuring the IV and impedance of the fuel cell stack for each m cycle, where m is a natural number less than or equal to n; and
(b6) terminating the information acquisition step for durability evaluation when the output voltage last measured in step (b5) is less than a preset certain ratio compared to the output voltage initially measured in step (b4).
Containing more,
method.
According to paragraph 3,
In step (b4), n is 100,
In step (b5), m is 30 to 50,
In step (b6), the preset constant ratio is 30% to 50%,
method.
According to paragraph 2,
In step (c),
(c1) dividing the fuel cell stack into two or three unit cells;
(c2) repeating steps (b1) to (b3) and measuring IV, impedance, cyclic voltammetry (CV), and linear sweep voltammetry (LSV) for each unit cell of the divided fuel cell stack;
(c3) evaluating the performance of each unit cell using the measured IV, impedance, CV, and LSV of each unit cell using a preset method;
(c4) confirming the thickness of the electrode and the thickness of the film using the cross-sections of the unit cells of the fuel cell stack divided into equal parts; and
(c5) Evaluating the degree of deterioration for each unit cell by comparing the thickness of the electrode and the thickness of the film for each confirmed unit cell.
Including,
method.
According to clause 5,
In step (c1) above,
Divide the fuel cell stack into two unit cells on the hydrogen inflow side and unit cells on the hydrogen outflow side, or
The fuel cell stack is divided into three parts: a hydrogen inlet unit cell, a central unit cell, and a hydrogen outflow unit cell.
method.
According to paragraph 3,
In step (d),
(d1) a durability evaluation step of evaluating the durability of the fuel cell stack by comparing the total number of cycles repeated from steps (b4) to (b5) and a preset reference number; and
(d2) calculating the lifespan of the fuel cell stack by multiplying the total number of cycles repeated from steps (b4) to (b5) by the average operating time of the device in which the fuel cell stack is used.
Including,
method.

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