KR20130066012A - Separator for fuel cell - Google Patents

Abstract

PURPOSE: A separator for fuel cell is provided to maximize area and number of channels without change of pattern and channel shape, thereby reducing resistance of material transfer resistance due to activation of reaction area. CONSTITUTION: A separator for fuel cells has an active area of 50cm^2. The channel area and land area are the same, or the channel area is larger than the land area. The separator is manufactured with 2:1 area ratio of the channel to the land. The active area of the separator for fuel cells is 50 cm^2. The channel area and land area in the separator are the same, or the channel area is larger than the land area while having 1-7 of channels. [Reference numerals] (AA) Ch 5 1:1 performance; (BB) Ch 5 2:1 performance; (CC) 360 performance; (DD) Ch 5 1:1 pressure; (EE) Ch 5 2:1 pressure; (FF) 360 pressure

Description

Separator for fuel cell

The present invention relates to a separator for a fuel cell, and more particularly, a fuel cell separator for improving fuel cell performance by optimizing the number of channels and the channel area without changing the flow path shape and pattern of a 50 cm2 separator. It is about.

Fuel cell vehicles are attracting attention as eco-friendly technologies that can realize energy independence and low carbon green growth by using hydrogen, a future energy source in preparation for exhaustion of petroleum resources in transportation energy.

In response to the growing interest in the environment, in response to the regulation of the total amount of carbon dioxide proposed by major industrialized countries, hydrogen fuel cell vehicles are a major response technology, and thus, various types of fuel cell vehicles have been developed and are showing close results to commercialization.

The fuel cell stack, which substantially generates electricity during the construction of the fuel cell system, has a membrane-electrode assembly (also referred to as a MEA, an electrode membrane assembly, and an electrode membrane assembly), a reaction path for conducting gases, and an electric conduction function. It has a structure in which dozens or hundreds or more of unit cells made up of separators are stacked, and both ends are equipped with end plates that fix each stacked component at a constant surface pressure and serve as current collectors.

At this time, the membrane-electrode assembly is a gas diffusion layer which is stacked on the outer surface of the polymer electrolyte membrane and the catalyst layer, the anode and cathode, the catalyst layer arranged with the polymer electrolyte membrane interposed therebetween, which serves to diffuse the reaction gases and remove the generated water. (GDL: Gas Diffusion Layer).

In addition, the separation plate includes an air side flow path serving as a passage of each reactor body, a hydrogen side flow path and a cooling flow path.

Briefly looking at the electricity generation principle of the fuel cell, the hydrogen is supplied to the anode of the fuel cell stack and the oxidation reaction of hydrogen at the anode proceeds to generate hydrogen ions (Proton) and electrons (Electron), and the generated hydrogen ions And electrons move to the cathode through the electrolyte membrane and the separator, respectively, and the cathode generates water through the electrochemical reaction involving hydrogen ions, electrons and oxygen in the air. The final generated electrical energy is supplied to a load (eg, a motor for driving a fuel cell vehicle) requiring electrical energy through the current collector plate of the end plate.

In the early stages of fuel cell development, attention was focused on the development of materials such as membrane electrode-assembly / gas diffusion layers (MEA / GDL) to increase the amount of electricity derived from the same fuel, ie to improve fuel economy. Taking into account aspects such as uniform distribution of flow, reduced flooding by generated water, and good electrical conductivity, the development of the separator can play a significant role in increasing performance and improving durability. Importance is on the rise.

On the other hand, the active area 50cm2 of the separator is an area established as a standard by the Department of Energy (DOE), which is the center of environmental energy research, and is a specification that has become an evaluation standard in academic fields and applications. Research is underway for the development of high power separators with a live area of 50cm2.

Referring to FIG. 1 attached to a separator structure having a smooth area of 50 cm 2, a gas inlet 11 to which gas such as air or hydrogen is supplied, and a channel 12 through which gas injected into the gas inlet 11 flows; And a gas outlet 13 through which the gas passing through the channel 12 is discharged, and a gasket 14 mounted on the outer portion for gastightness.

In FIG. 1, the gas inputted into the gas inlet 11 indicated by the red circle is moved along each channel 12 and finally discharged through the gas outlet 13, where the gas is discharged through the membrane electrode in each channel. It is supplied to all areas of the assembly.

The channel structure of the separator can be modified in various forms according to the operating conditions and the use characteristics of the fuel cell, and when the channel shape and pattern are changed under the same experimental conditions, a performance difference of up to 50% or more is eventually obtained. Depending on the design of the separator, efficient reactor diffusion and water management will vary and fuel cell performance will vary.

The present invention has been made in view of the above, and the reaction of the membrane-electrode assembly to the catalyst layer by controlling the number of channels and increasing the channel area without changing the flow path shape and pattern of the active area 50 cm 2 separator plate It is an object of the present invention to provide a separator for fuel cells that can increase the area of the fuel cell and increase the performance of the fuel cell by reducing the material transfer resistance due to the activation of the reaction area.

In order to achieve the above object, the present invention provides a fuel cell separator having a large area of 50 cm2, wherein the channel area and land area of the separator plate are the same or the channel area is larger than the land area, and the number of channels is three. Provided is a separator for a fuel cell, characterized in that formed from seven to seven.

Preferably, the area ratio between the channel and the land is produced in a 2: 1 ratio.

More preferably, it is characterized in that the channel of the separator is formed of three channels.

In addition, when the number of channels is formed into three channels, the channel length and the number of turns of the channels are increased and the total cross-sectional area of the channels is reduced.

Through the above-mentioned means for solving the problems, the present invention provides the following effects.

According to the present invention, by controlling the number of channels and increasing the channel area without changing the flow channel shape and pattern of the active area 50 cm 2 separator plate, the reaction area is increased due to the increase of the reaction area with respect to the catalyst layer of the membrane-electrode assembly. By reducing the material transfer resistance, the performance of the fuel cell can be increased.

In addition, by adjusting the gas supply pressure by adjusting the number of channels, it is possible to prevent the power density decrease due to the water flooding phenomenon generated during the fuel cell reaction.

In addition, the gas supply pressure is increased to facilitate the discharge of water, the reactants hydrogen and oxygen are evenly transferred from the inlet to the outlet of the channel, and the electrochemical reaction occurs at the entire activation area, thereby improving the power density. Therefore, the fuel cell volume can be reduced while the cost of power production can be lowered.

1 is a cross-sectional view showing a structure of the active area 50 cm 2 separator plate,
Figure 2 is a schematic diagram showing a gas supply process of the separator,
3 is a graph showing the gas supply pressure and the fuel cell performance according to the separation plate channel area ratio of the present invention;
Figure 4 is a graph measuring the impedance according to the channel area ratio of the separator of the present invention,
5 is a graph showing the gas supply pressure and fuel cell performance according to the number of channels of the separator plate of the present invention;
Figure 6 is a graph measuring the impedance according to the number of channel divider of the present invention,
7 is a schematic diagram illustrating liquid discharge according to a channel inlet and outlet pressure difference.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

As described above, studies to change the channel shape and pattern of the separator as a method for improving the performance of the membrane-electrode assembly have been generally conducted. The main point is to improve the performance of the membrane-electrode assembly.

First, to assist in understanding the present invention, the gas supply process in the fuel cell stack will be described with reference to FIG. 2 as follows.

An anode and a cathode, which are the catalyst layer 22, are stacked with the polymer electrolyte membrane 20 interposed therebetween (only the cathode side is shown in FIG. 2), and diffusion of reaction gases and removal of generated water on the outer surface of the catalyst layer 22, etc. A gas diffusion layer 24 serving as a stack is stacked, and a separation plate 10 is stacked outside the gas diffusion layer 24.

In this case, the inner surface of the separation plate 10 is formed with a channel 15 which is a path for gas flow and a land 15 closely supported by the gas diffusion layer 24.

Thus, after gas (hydrogen or air) flows through the channel and diffuses through the gas diffusion layer, it is supplied to the membrane-electrode assembly for reaction for generating electricity, and the portion hatched in a circle in FIG. 2 is in close contact with the land. It represents a dead zone in which gas does not diffuse smoothly.

The present invention can improve the performance of the membrane-electrode assembly by adjusting the area ratio between the channel area facing the membrane-electrode assembly and the lands in contact with the gas diffusion layer without changing the channel shape and pattern of the separator having the above function. In consideration of the fact that the performance changes according to the increase in gas supply pressure and the increase in the number of channels, the performance of the membrane-electrode assembly can be increased.

Here, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

Examples 1 and 2

As shown in Table 1, the area ratios of the channels and lands of the five-channel separator having the same channel structure and pattern are 1: 1 (Example 1) and 2: 1 (implemented) using the separator having a total active area of 50 cm 2. Made to Example 2).

Substantially, the area ratios of the channels and the lands of the five-channel separation plate were manufactured at 1.08: 1 (Example 1) and 2.00: 1 (Example 2).

Comparative Example 1

As a comparative example, a conventional large area separator (360 cm 2) was produced.

Experimental Example 1

The separation plates according to Examples 1 and 2, and the large-area separation plates according to the comparative example were manufactured by manufacturing the area ratios of the channels and the lands of the five-channel separation plates to 1.08: 1 and 2.00: 1, The performance (potential) and gas supply pressure measurement tests of the membrane-electrode assembly were performed, and the results are shown in the accompanying graph of FIG. 3 and Table 2 below.

As shown in the graph and Table 2 of FIG. 3, the separators according to Example 1 and Example 2 are both lower in pressure than the large-area separator according to the comparative example, but have an area ratio of 2: 1 between the channel and the land. It was found that the performance (potential) of the separator according to Example 2 was higher than that of the large area separator.

On the other hand, in the case of the five-channel separator according to Example 1 manufactured at a ratio of 1: 1, the gas supply pressure is similar to the five-channel separator according to Example 2 manufactured at 2: 1, but the performance (potential) is It was found to be lower than the large area separator.

As a result, the channel area (surface facing the catalyst layer of the membrane-electrode assembly) of the 5-channel separator fabricated 2: 1 according to Example 2 of the present invention is separated into 5-channel fabricated 1: 1. As it is wider than the plate, it was found that the electrode (catalyst layer) active area of the membrane-electrode assembly which can be in direct contact with the gas is increased, thereby improving performance and gas supply pressure.

Experimental Example 2

Impedance was measured for the separators according to Examples 1 and 2, in which the area ratios of the channels and lands of the five-channel separator were 1.08: 1 and 2.00: 1, and the results are shown in the graph of FIG. As shown.

As shown in the graph of Figure 4, the separation plate according to the first and second embodiments according to the change in the cell resistance is insignificant, as the land area is reduced it can be seen that the change in contact resistance has less effect on the performance, the material transfer resistance It can be seen that the value is a significant difference.

As a result, in the separator according to Example 2, it can be seen that as the channel area is increased, the active area of the electrode (catalyst layer) with the increased contact area with the gas increases and the electrochemical reaction active site increases. It was confirmed by the decrease in resistance.

On the other hand, referring to Figure 2 showing a gas supply schematic diagram of the separation plate, in the case of a separation plate having a large land area, the dead zone occurs because the gas does not diffuse into the gas diffusion layer of the portion pressed in contact with the land portion, Figure 2 As shown on the right side of the separator, in the case of a separator having a narrow land area, gas may diffuse to the gas diffusion layer under the land, which increases the channel area as described above, thereby increasing the electrical active area of the membrane-electrode assembly. It can be attributed to the high performance of the separator having a high ratio of channel area to land ratio.

Examples 3-5

The channel: land area ratio of the separator plate was uniformly fixed at 1: 1, and as shown in Table 3 below, only the number of channels was adjusted to prepare a separator plate.

As shown in Table 3, the separation plate of three channels was manufactured by setting the channel length 780.18mm and the channel: land area ratio 0.98: 1 as Example 3, and the channel length 495.02mm and the channel: land area ratio 1.08 as Example 4 The separation plate of five channels was produced as 1: 1, and the separation plate of seven channels was produced as Example 5 with a channel length of 354.23 mm and a channel-land area ratio of 1.08: 1.

At this time, even at the same flow rate, the supply pressure varies depending on the increase and decrease of the number of channels.

That is, when the input flow rate is 10 lpm [Liter per minite], the three channel separator according to Example 3 is injected with a gas of 3.33 lpm for each channel, the five channel separator according to Example 4 is 2 per channel The lpm, seven-channel separator is supplied with 1.42 lpm of gas per channel.

This decrease in the number of channels means that the channel length is longer, the number of turns is increased, and the total cross-sectional area of the channel through which the supply gas must pass is reduced, thereby increasing the gas supply pressure.

Experimental Example 3

In order to confirm that the gas supply pressure is an important factor that affects the performance of each cell of the fuel cell by adjusting the number of channels, the performance trend and performance change factors that resulted from the change of the gas supply pressure through the channel number of the cell were measured. The results are as shown in the attached graph and table 4 of FIG.

5 is a performance and supply pressure curve of the 3, 7, 9-channel separator plate cell, it can be seen that the cell supply pressure (gas supply pressure) of the three-channel separator plate according to Example 3 has the highest and the cell performance is also the highest. As the number of channels decreases, the cell supply pressure increases, and as a result, the cell performance also increases.

In particular, the cell performance increases toward the high current region, which means that the greater the pressure difference between the inlet and the outlet of the channel, the higher the ability to discharge the generated liquid water, thereby decreasing the material transfer resistance and thus increasing the performance.

That is, as shown in the conceptual diagram of FIG. 7, when the inlet and outlet pressure difference of the channel is large, the water moving distance is large, and thus the ability to discharge the water in the channel is increased, which means that the performance is increased by reducing the material transfer resistance. will be.

Experimental Example 4

Since the factor of increasing cell performance (contact resistance, material transfer resistance, etc.) can be confirmed by impedance measurement, impedance measurement in a high current region was performed for the separator plates according to Examples 3 to 5, and the result is shown in FIG. As shown in the graph.

6 is impedance data measured at 1600 mA / cm 2, and the magnitude of the material transfer resistance was 7 channels> 5 channels> 3 channels.

That is, it can be seen that the material transfer resistance of the three-channel separator according to the third embodiment of the present invention is relatively low compared to the material transfer resistance of the other two separators, which is enough to discharge the generated water due to the pressure difference between the inlet and outlet of the channel. As a result, the flooding is reduced, which causes a difference in material transfer resistance, which may result in a change in performance.

10: Separator
11: gas inlet
12: channel
13 gas outlet
14: Gasket
15; rand
20: polymer electrolyte membrane
22: catalyst layer
24 gas diffusion layer

Claims (7)

In a fuel cell separator having a live area of 50 cm 2,
Separating plate for fuel cells, characterized in that the channel area and the land area of the separation plate is formed to be the same or the channel area is larger than the land area.
The method according to claim 1,
Separation plate for a fuel cell, characterized in that the area ratio between the channel and the land produced in a 2: 1 ratio.
The method according to claim 1,
Separation plate for a fuel cell, characterized in that the area ratio between the channel and the land produced in a ratio of 1.8: 1.
The method according to claim 1,
Separation plate for a fuel cell, characterized in that the area ratio between the channel and the land produced in a ratio of 2.2: 1.
In a fuel cell separator having a live area of 50 cm 2,
Separation plate for a fuel cell, characterized in that the channel area and the land area of the separator to be formed the same or the channel area is larger than the land area and the number of channels is formed from 1 to 7.
The method according to claim 5,
Separation plate for a fuel cell, characterized in that the channel of the separating plate formed of three channels.
The method according to claim 5 or 6,
When the channel number is formed into three channels, the channel cross-section and the number of turns of the channel is increased at the same time the total cross-sectional area of the channel is reduced.

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