KR20100138424A - Device and method for inspecting defective mea of fuel cell - Google Patents

Abstract

PURPOSE: A pre-detection apparatus for an electrode membrane assembly of a fuel cell, and a method thereof are provided to detect a hydrogen crossover phenomenon of the electrode membrane assembly before manufacturing the fuel cell. CONSTITUTION: A pre-detection apparatus for an electrode membrane assembly(10) of a fuel cell comprises the following: an upper fixing plate(20) with a measurement terminal(23) on the outer surface, installed on the upper side of the electrode membrane assembly; a lower fixing plate(22) with another measurement terminal(24), attached to the bottom of the electrode membrane assembly; and a coupling vice combined with the upper and lower fixing plates to secure the gas air tightness.

Description

Device and method for inspecting defective MEA of fuel cell

The present invention relates to an electrode membrane assembly pre-inspection apparatus and method for a fuel cell, and more particularly, electrode membrane assembly prior to fabrication of a fuel cell, such as determining whether an electrical short of the electrode membrane assembly (MEA) and hydrogen crossover phenomenon. The present invention relates to a fuel cell electrode membrane assembly pre-inspection apparatus and method for preliminary inspection to prevent a defective electrode membrane assembly from being mounted on a fuel cell vehicle.

Compared with other types of fuel cells, the polymer electrolyte fuel cell has the advantages of high efficiency, high current density and power density, short start-up time, and solid electrolyte, which does not require corrosion and electrolyte control. Since it emits only pure water, it is attracting attention as an environmentally friendly future power source.

In general, an electrode membrane (MEA: Membrane-Electrode Assembly), which is a main component, is located at the innermost side of a fuel cell stack mounted in a fuel cell vehicle, as shown in FIG. 7A. The membrane assembly includes a solid polymer electrolyte membrane 12 capable of moving protons, and a catalyst layer coated on both surfaces of the electrolyte membrane such that hydrogen and oxygen can react, that is, an air electrode 14 and a fuel electrode ( 16: Anode)

In addition, a gas diffusion layer (GDL), a gasket, and the like are stacked on an outer portion of the electrode layer, that is, an outer portion where a cathode and an anode are located, and a fuel is disposed on an outer side of the gas diffusion layer. A separator having a flow field is formed to supply and discharge the water generated by the reaction, and an outer plate is coupled to the outermost end plate for supporting the above components.

The polymer electrolyte fuel cell is a device that generates electricity while generating water and heat through an electrochemical reaction between hydrogen and oxygen. The supplied hydrogen is separated into hydrogen ions and electrons in the catalyst of the anode electrode, and is separated. Hydrogen ions pass through the electrolyte membrane to the cathode, where they combine with the supplied oxygen and electrons from the external conductor to generate water while generating water.

The theoretical potential generated at this time is about 1.3V and the reaction formula is as follows.

^{_{Anode: H 2 → 2H + +}} 2e -

^{_{Cathode: 1/2 O 2 + 2H +}} + 2e - → H 2 O

In actual fuel cell vehicles, the voltage is between 0.97 and 1.1V even though no current is applied due to hydrogen crossover.

In this case, the hydrogen crossover refers to a phenomenon in which oxygen due to partial pressure penetrates into the air electrode and crosses the fuel electrode when the fuel cell shuts down. This hydrogen crossover phenomenon causes abnormal water generation in the anode along with the fuel cell start-up. This results in catalyst detachment due to carbon support and carbon corrosion.

The voltage formed in the fuel cell is the potential difference between the cathode and the anode, and this voltage is called an open circuit voltage (OCV), and this OCV may not have any external current applied to the fuel cell. The voltage at the time is affected by the concentration of the gas used in the fuel electrode and the air electrode.

However, when a current flows inside the fuel cell, the OCV decreases by the amount of current flowing, which is caused by a hydrogen crossover and is generated by a chemical reaction, and its value is a normal electrode membrane assembly (MEA). ) Is constant within about 2mA / ㎠.

However, in the case of an abnormal electrode membrane assembly (MEA), a current value generated therein may be higher than 2 mA / cm 2. When the root cause is analyzed, the membrane used in the electrode membrane assembly is damaged and hydrogen is lost. It can be seen that the amount of crossover is increased or electrical contact occurs in most cases.

In particular, the main cause of the electric current generated by the electrical contact is due to the penetration of the carbon material of the gas diffusion layer 18 (GDL) used in the electrode membrane assembly 10 into the membrane, as indicated by the arrows in FIG. 7B. This is because both gas diffusion layers contact each other.

Usually, the gas diffusion layer consists of carbon paper and is a conductor material.

Therefore, when fabricating a 5-layer electrode membrane assembly, if the catalyst layer and the membrane are damaged due to a poor surface of the gas diffusion layer, both gas diffusion layers may come into contact with each other to generate excessive current inside the cell. .

The flow of internal current due to such damage not only lowers the OCV value, but also the membrane may be gradually weakened by the gas diffusion layer penetrated. Consequently, the electrical short-circuit caused by the internal current of the cell may damage the electrode membrane assembly. Starting up a fuel cell vehicle results in the failure of OCV formation, making the vehicle impossible to operate.

Accordingly, a procedure for checking whether the state of the electrode membrane assembly is normal or abnormal (defective) is required through prior inspection before the actual electrode membrane assembly is mounted on the vehicle.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described aspects, and includes an electrode before mounting a vehicle or manufacturing a fuel cell such as determining an electric short phenomenon in an electrode membrane assembly by a gas diffusion layer and confirming a hydrogen crossover phenomenon. It is an object of the present invention to provide a fuel cell electrode membrane assembly pre-inspection apparatus and method for preliminary inspection of a membrane assembly to prevent abnormal mounting of the electrode membrane assembly in a fuel cell vehicle.

The present invention for achieving the above object is a structure in which the measurement terminal is integrally formed on the outer surface, and the hydrogen and nitrogen inlet and outlet are formed, the upper fixing plate which is in close contact with the upper surface of the electrode film assembly to be measured; A lower fixing plate formed integrally with the measurement terminal on the outer surface and in close contact with the bottom surface of the electrode film assembly to be measured; A fastening vise detachably coupled to edges of the upper and lower fixing plates for gas tightness of the electrode membrane assembly; A potential difference measuring device connected to the measurement terminal to apply a voltage to an electrode film assembly and measure a potential difference; It provides an electrode membrane assembly pre-inspection apparatus for a fuel cell, characterized in that configured to include.

In a preferred embodiment, two or more electrode film assemblies to be laminated between the upper and lower fixing plates are laminated with an insulating plate having a hydrogen inlet and outlet therebetween.

The present invention for achieving the above object comprises the steps of injecting hydrogen and nitrogen gas to the electrode film assembly of the measurement object to be laminated while maintaining the airtight in a predetermined measurement structure; Applying a voltage to the electrode film assembly at a constant speed and range so that a current is generated in the electrode film assembly; Measuring a current density generated in the electrode film assembly and determining that a hydrogen crossover has occurred in the electrode film assembly if it is greater than or equal to a threshold value; It provides a fuel cell electrode membrane assembly pre-inspection method comprising a.

In a preferred embodiment, if the amount of current generated in the electrode film assembly to be measured continuously increases, further comprising the step of determining that both the gas diffusion layer in the electrode film assembly is in contact with each other to generate an electrical short do.

In a more preferred embodiment, when using a device for applying a high voltage to the electrode film assembly, it is characterized in that the hydrogen crossover and electrical short pre-inspection of the plurality of electrode film assemblies stacked with the insulating means in between It is done.

Through the above problem solving means, the present invention provides the following effects.

According to the present invention, it is possible to prevent the abnormal mounting of the electrode membrane assembly in the fuel cell vehicle by checking whether the electrode membrane assembly is electrically shorted and the hydrogen crossover phenomenon before the production of the fuel cell.

Therefore, when an abnormal electrode membrane assembly is used, it is possible to reduce the time and human loss of removing and repairing the fuel cell stack in the fuel cell vehicle.

In addition, the quality control of the fuel cell unit may be performed through the prior inspection of the electrode membrane assembly, and when an abnormal cell is detected, the detected cell may be used as a means for cause analysis.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As described above, conventionally, after the electrode membrane assembly is assembled into the fuel cell stack and before mounting in the fuel cell vehicle, internal current flows due to an electrical short phenomenon inside the electrode membrane assembly or excessive hydrogen crossover due to membrane damage. If the abnormal electrode membrane assembly is mounted on the fuel cell vehicle because the phenomenon is not detected, the fuel cell stack may be defective. As a result, the operation of the vehicle may be stopped due to the phenomenon that the cell voltage is lowered during the operation of the fuel cell vehicle. There was a problem that occurred, and when such a problem occurred, the human and time loss caused by removing the entire fuel cell stack from the vehicle and replacing the cell in question.

In view of this, the present invention is to determine whether the electrical short of the electrode membrane assembly and the hydrogen crossover phenomenon in advance to check the electrode membrane assembly for fuel cells that can prevent the abnormal mounting of the electrode membrane assembly in the fuel cell vehicle in advance. It is to provide a pre-inspection apparatus and method.

Electrode membrane assembly pre-inspection apparatus of the present invention for this purpose is as shown in Figures 1 and 2 attached.

Electrode membrane assembly pre-inspection apparatus according to the present invention for determining the abnormality of the electrode membrane assembly of the fuel cell, and the conductive upper and lower fixing plates (20, 22) for fixing the electrode membrane assembly 10 and The upper and lower fixing plates 20 and 22 to be immobilized, and at the same time, the fastening vise 30 having a gas-tight function and a potential difference measuring device 40 for measuring a potential difference while applying a voltage to the electrode membrane assembly 10. And the like.

The upper and lower fixing plates 20 and 22 are an electrode membrane assembly 10, that is, an electrolyte membrane 12 (membrane), and an air electrode 14, which is a catalyst layer coated to react hydrogen and oxygen on both surfaces of the electrolyte membrane 12. , 5-layer MEA having a 5-layer structure consisting of a cathode and an anode 16 and a gas diffusion layer 18 and GDL stacked on the outside of the cathode 14 and the anode 16. As a plate-like plate structure made of a conductive material, the measuring terminals 23 and 24 for voltage application and current measurement are integrally formed on each outer surface.

In addition, a pair of gas inlets and outlets 25, 26, 27, and 28 are formed at both ends of the upper fixing plate 20, respectively, and a hydrogen inlet 25 and a nitrogen outlet 28 are formed at one side thereof. On the other side, a hydrogen outlet 26 and a nitrogen inlet 27 are formed.

Therefore, the electrode membrane assembly (injecting and circulating hydrogen and nitrogen gas through the gas inlets and outlets 25, 26, 27, and 28 while the electrode membrane assembly 10 is embedded between the upper and lower fixing plates 20 and 22). 10) is tested for abnormality, and the side of the electrode membrane assembly 10 disposed between the upper and lower fixing plates 20 and 22 is in an open state and should be sealed for gas tightness.

Thus, in the present invention, while firmly fixing the upper and lower fixing plate while pressing the upper edge of the upper fixing plate 20 and the lower edge of the lower fixing plate at the same time to seal the open side of the electrode membrane assembly (10). A separate fastening vise 30 is adopted.

The fastening vise 30 is a rectangular frame structure having a cross-sectional structure of "c", and the upper and lower push ends 32 and 34 arranged horizontally have a top edge of the upper fixing plate 20 and a bottom edge of the lower fixing plate 22. Presses, and the connecting end 36 between the upper and lower pressing ends 32 and 34 serves to seal the open side of the electrode membrane assembly 10.

Preferably, as shown in the accompanying FIG. 1, the upper pressing end 32 is manufactured separately, so that the upper end of the connecting end 36 may be assembled by bolting or the like.

Here, the pre-inspection method based on the electrode membrane assembly pre-inspection apparatus for a fuel cell of the present invention having the above configuration will be described in order.

First, the electrode film assembly 10 to be measured, that is, the electrode film assembly having a five-layer structure, is embedded between the upper and lower fixing plates 20 and 22 as described above. The lower fixing plates 20 and 22 are fastened and fixed at a constant force, and the electrode membrane assembly 10 is sealed.

In this state, hydrogen and nitrogen gas are supplied through the hydrogen inlet 25 and the nitrogen inlet 27 of the upper fixing plate 20.

The purpose of using nitrogen is to take only the current generated by electrical contact and the current generated only by hydrogen crossover while preventing the electrochemical reaction at the electrode.

In this case, as shown in FIG. 3, the potential difference measuring device 40 is connected to the measurement terminals 23 and 24 for voltage application and current measurement integrally formed on the upper and lower fixing plates 20 and 22. The voltage is applied to the electrode film assembly 10 up to a constant speed and range in the potential difference measuring device 40, and the electrode film assembly 10 generates a current due to the voltage application.

If the electrode membrane assembly 10 used for the measurement is normal, it has a constant current density of about 2mA / ㎠ as shown by 1 of Figure 5 attached, but in the case of the abnormal electrode membrane assembly having a problem hydrogen cross The over occurs excessively, resulting in a much larger amount of current than 2 mA / cm 2, which is the current generated in the normal cell, as indicated by 2 in FIG. 5.

Thus, if the measurement resulted in a current density higher than about 2 mA / cm 2, it is considered that excessive hydrogen crossover occurred in the electrode film assembly to be measured.

In addition, in the electrode film assembly 10 to be measured, when electrical contact occurs by the carbon material of the gas diffusion layer, as shown in FIG. 6, the amount of internal generated current continues to increase linearly as the voltage increases. Done.

Therefore, as shown in FIG. 6, the increase in the generated current in the electrode film assembly 10 may be said to be caused by the electrical diffusion of both gas diffusion layers corresponding to the conductors to each other. This can be the case when the carbonaceous material of the gas diffusion layer has penetrated the membrane.

Accordingly, if the generated current in the electrode film assembly 10 to be measured continues to increase linearly, it can be determined that the carbon material of the gas diffusion layer penetrates the membrane and both gas diffusion layers are in contact with each other. It can be ascertained that the electrode film assembly determined before assembly to the battery stack and mounted in the vehicle is defective.

On the other hand, if the specification of the voltage application equipment for the electrode film assembly 10 to be measured up to about 100V, it is possible to check the bad electrode film assembly in advance by measuring several electrode film assemblies up to 130 at the same time.

That is, as shown in the attached 4, between the upper and lower fixing plates 20 and 22, various electrode film assemblies 10 to be measured are interposed between the insulating plate 50 having hydrogen and nitrogen inlets (not shown). After stacking, and fastening and fixing the upper and lower fixing plates 20 and 22 by using the fastening vise 30, hydrogen and nitrogen gas through the hydrogen inlet 25 and the nitrogen inlet 27 of the upper fixing plate 20. In the state of supplying, increasing the voltage application specification up to 100V can measure the current for up to 130 electrode assemblies 10 and at the same time pre-inspection.

As described above, according to the fuel cell electrode membrane assembly pre-inspection apparatus and method of the present invention, the electrical short phenomenon and hydrogen crossover phenomenon of the electrode membrane assembly can be inspected in advance to reduce the failure rate of the fuel cell stack, The time and labor costs of replacing the abnormal fuel cell stack can be dramatically reduced.

1 and 2 are a cross-sectional view and a plan view showing an electrode membrane assembly pre-inspection apparatus according to the present invention;

3 and 4 are cross-sectional views illustrating a process of performing the inspection of the electrode membrane assembly according to the present invention;

5 and 6 are graphs illustrating the electrode membrane assembly pre-inspection result according to the present invention;

7A and 7B are schematic views illustrating the configuration of the electrode film assembly and its problems.

<Explanation of symbols for the main parts of the drawings>

10 electrode assembly 12 electrolyte membrane

14: air electrode 16: fuel electrode

18 gas diffusion layer 20 upper fixing plate

22: lower fixing plate 23, 24: measuring terminal

25: hydrogen inlet 26: hydrogen outlet

27: nitrogen inlet 28: nitrogen outlet

30: tightening vise 32: upper pressing end

34: lower pressing end 36: connecting end

40: potential difference measuring instrument 50: insulating plate

Claims (5)

An upper fixing plate which is integrally formed on the outer surface of the measuring terminal and formed with hydrogen and nitrogen inlets and outlets, the upper fixing plate being in close contact with the upper surface of the electrode film assembly to be measured; A lower fixing plate formed integrally with the measurement terminal on the outer surface and in close contact with the bottom surface of the electrode film assembly to be measured; A fastening vise detachably coupled to edges of the upper and lower fixing plates for gas tightness of the electrode membrane assembly; A potential difference measuring device connected to the measurement terminal to apply a voltage to an electrode film assembly and measure a potential difference; Electrode membrane assembly pre-inspection apparatus for a fuel cell, characterized in that configured to include. The method according to claim 1, An electrode membrane assembly pre-inspection apparatus for a fuel cell, wherein at least two electrode membrane assemblies to be stacked between the upper and lower fixing plates are stacked with an insulating plate having a hydrogen inlet and outlet interposed therebetween. Injecting hydrogen and nitrogen gas into the stacked electrode film assemblies while maintaining airtightness within a predetermined measurement structure; Applying a voltage to the electrode film assembly at a constant speed and range so that a current is generated in the electrode film assembly; Measuring a current density generated in the electrode film assembly and determining that a hydrogen crossover has occurred in the electrode film assembly if it is greater than or equal to a threshold value; An electrode membrane assembly pre-inspection method for a fuel cell, characterized in that consisting of. The method according to claim 3, And if the amount of current generated in the electrode film assembly to be measured is continuously increased, determining that an electric short is generated by contacting both gas diffusion layers in the electrode film assembly. Assembly pre-inspection method. The method according to claim 3, In the case of using a device for applying a high voltage to the electrode membrane assembly, an electrode membrane for a fuel cell, which performs hydrogen crossover and electrical short pre-inspection of several electrode membrane assemblies stacked with insulating means at once. Assembly pre-inspection method.

Images