JP2010212216A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell in which deterioration of power generation performance can be suppressed by improving a problem that the cooling condition of two MEA(s) becomes uneven in a structure of 2-cell 1-cooling type. <P>SOLUTION: The fuel cell has a 2-cell 1-cooling type structure in which separators 302, 304, a left-hand side unit cell 10, an intermediate separator 306, a right-hand side unit cell 110, and separators 308, 310 are laminated in this order, and the concave depth D<SB>1</SB>of the separator 304 is made shallower than the concave depth D<SB>2</SB>of the intermediate separator 306. Thereby, the total cross-section area of passage of the outside separator 304 is made smaller than the total cross-section area of the passage of the intermediate separator 306, and the wet condition in the anode side face of the second membrane electrode assembly 110 is kept excellently, and deterioration of the power generation performance can be suppressed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-87311, a two-cell, one-cooled fuel cell is known. “Two-cell one-cooled fuel cell” means two MEAs (Membrane Electrode Assembly) and one refrigerant as illustrated in FIG. 1 and FIG. 8 of JP-A-2004-87311. It refers to a fuel cell having a structure in which flow paths are alternately stacked.

JP 2004-87311 A JP 2000-208153 A

  In the 2-cell 1-cooled fuel cell, the cooling state of the two MEAs becomes uneven. Specifically, the anode side is actively cooled in one of the two MEAs, and the cathode side is actively cooled in the other MEA. In the 2-cell 1-cooled fuel cell, a specific problem occurs due to such a difference in the cooling conditions. As a result, the power generation performance of the fuel cell may be reduced.

  The present invention has been made to solve the above-described problems, and provides a fuel cell capable of improving the overall configuration in a two-cell, one-cooled configuration and suppressing a decrease in power generation performance. With the goal.

In order to achieve the above object, a first invention is a fuel cell,
A first membrane electrode assembly comprising: an electrolyte membrane; an anode electrode catalyst layer provided on one surface of the electrolyte membrane; and a cathode electrode catalyst layer provided on the other surface of the electrolyte membrane;
An electrolyte membrane disposed on the cathode electrode catalyst layer side of the first membrane electrode assembly, an anode electrode catalyst layer provided on a surface of the electrolyte membrane on the first membrane electrode assembly side, and the electrolyte membrane A cathode electrode catalyst layer provided on the other surface of the second membrane electrode assembly,
A plurality of recesses interposed between the first and second membrane electrode assemblies, and a merging portion where the plurality of recesses merge are provided on the respective surfaces of the first and second membrane electrode assemblies. An intermediate separator provided,
The first membrane electrode assembly is disposed on the anode catalyst layer side, and a plurality of recesses and a junction where the plurality of recesses merge together are connected to the anode catalyst layer side on the first membrane electrode assembly side. An outer separator provided on the facing surface;
A coolant channel positioned so as to sandwich the first membrane electrode assembly, the intermediate separator, and the second membrane electrode assembly;
With
The concave channel total cross-sectional area of the outer separator <the concave channel total cross-sectional area of the intermediate separator on the second membrane electrode assembly side; and
A configuration in which the flow path cross-sectional area of the merging portion of the outer separator <the flow channel cross-sectional area of the merging portion on the second membrane electrode assembly side of the intermediate separator;
It comprises at least one structure among these.

  According to the first aspect of the present invention, when the fuel gas is caused to flow through the recess of the outer separator and the recess of the intermediate separator on the second membrane electrode assembly side, the flow rate of fuel gas at the anode of the second membrane electrode assembly Can be relatively increased. Thereby, the capability of transporting moisture in the anode side surface of the second membrane electrode assembly can be improved. As a result, the wet state in the anode side surface of the second membrane electrode assembly can be kept good, and the decrease in power generation performance can be suppressed.

It is sectional drawing which shows the structure of the fuel cell concerning Embodiment 1 of this invention. It is a figure which shows the result of the temperature characteristic test simulation which this inventor performed. It is a figure which shows the relationship between the anode gas flow volume and cell voltage in specific cell temperature. It is a disassembled perspective view which shows the structure of the fuel cell concerning Embodiment 2 of this invention. It is a figure which shows the structure of the fuel cell concerning Embodiment 3 of this invention.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a cross-sectional view showing a configuration of a fuel cell according to Embodiment 1 of the present invention. As shown in FIG. 1, the fuel cell of Embodiment 1 includes separators 302 and 304, unit cells 10 (hereinafter, also referred to as “left unit cell 10” for convenience of explanation), intermediate separators 306, unit cells 110 (hereinafter, For convenience of explanation, it is also referred to as “right unit cell 110”), and a two-cell, one-cooled configuration in which separators 308 and 310 are stacked in this order. Although not shown, in the first embodiment, one fuel cell stack is formed by repeatedly stacking this two-cell, one-cooled configuration in units of several hundreds. Each of the left unit cell 10 and the right unit cell 110 has an anode configuration on the left side of the paper and a cathode configuration on the right side of the paper. Each separator has an uneven shape.

  The left unit cell 10 includes an MEA (Membrane Electrode Assembly) in which electrode catalyst layers 14 and 20 are laminated on each surface of the solid polymer electrolyte membrane 12, and gas diffusion layers 16 and 22 made of carbon sheets or the like. Is provided. The plurality of recesses opened on the gas diffusion layer 16 side of the separator 304 each function as a gas flow path 18 for flowing hydrogen. The plurality of recesses opened on the gas diffusion layer 122 side of the intermediate separator 306 function as gas flow paths 24 for flowing air. The intermediate separator 306 has an uneven shape in which the unevenness is inverted between the front surface and the back surface. Similarly to the left unit cell 10, the right unit cell 110 also includes an MEA in which electrode catalyst layers 114 and 120 are laminated on each surface of the solid polymer electrolyte membrane 112, and gas diffusion layers 116 and 122. Similarly, a plurality of gas flow paths 118 for hydrogen and a plurality of gas flow paths 124 for air are provided. A plurality of coolant flow paths 300 are formed between the separators 302 and 304, and a plurality of coolant flow paths 312 are formed between the separators 308 and 310, respectively.

  The gas flow paths 18, 24, 118, 124 and the coolant flow paths 300, 312 respectively extend in the paper surface penetration direction in FIG. 1. Each flow path includes a merging portion on the front side in FIG. 1 and the back side in FIG. Of these merging portions, one merging portion is connected to an inlet for gas or cooling liquid, and the other merging portion is connected to an outlet for gas or cooling liquid. Although not shown, the gas inlet and the gas outlet are connected to an anode manifold or a cathode manifold extending in the fuel cell stack. The fuel cell of Embodiment 1 is assumed to be a fuel cell (so-called counter flow type fuel cell) in which the flow of hydrogen and air are opposed in the plane of the MEA.

As shown in FIG. 1, in the first embodiment, the concave depth D ₁ of the separator 304 is made shallower than the concave depth D ₂ of the intermediate separator 306 (D ₁ <D ₂ ). Thereby, the pressure loss of hydrogen at the anode of the left unit cell 10 can be made higher than the pressure loss of hydrogen at the anode of the right unit cell 110. Accordingly, the hydrogen flow rate of the anode of the right unit cell 110 (hydrogen flow rate of the gas flow channel 118) is increased as compared with the flow rate of hydrogen of the anode of the left unit cell 10 (hydrogen flow rate of the gas flow channel 18). Can do. In the first embodiment, the ratio is D ₁ : D ₂ = 1.0: 1.1. As a result, the flow rate ratio becomes 1.1 ² : 1.0 ² ≈1.2: 1.0, and the stoichiometric ratio can be 1.44: 1.2.

[Effects of First Embodiment]
Hereinafter, the function and effect of the first embodiment will be described. According to the first embodiment, hydrogen gas flows through the gas flow path 18 and the gas flow path 24. The anode side of the right unit cell 110 faces the intermediate separator 306 and is separated from the coolant flow paths 300 and 312. Conversely, the anode side of the left unit cell 10 is adjacent to the coolant channel 300 and is easily cooled. As a result, the temperature during power generation is higher on the anode side of the right unit cell 110 than on the anode side of the left unit cell 10. If there is unevenness of such a cooling condition, if the凹深of D ₂ of凹深of D ₁ and the intermediate separator 306 in the case where the gas flow path structure of the unit cells 10, 110 in the same (i.e. separator 304 ) In the right unit cell 110, there is a risk of moisture shortage on the anode side, particularly on the downstream side of the hydrogen flow. In this regard, according to the first embodiment, the hydrogen flow rate of the anode of the right unit cell 110 can be relatively increased. As a result, it is possible to increase the water carrying capacity and spread the moisture into the anode side surface of the right unit cell 110. As a result, a decrease in power generation performance can be suppressed. In the case of a fuel cell in which the inlet and outlet are opposed to each other at the anode and the cathode (especially in the case of a counter flow type fuel cell), there is moisture transfer from the cathode through the electrolyte membrane on the gas inlet side of the anode. On the contrary, the gas outlet side of the anode faces the gas inlet side of the cathode, which is easy to dry, and therefore moisture tends to be insufficient. The first embodiment is particularly suitable for such a case.

  FIG. 2 shows the results of a temperature characteristic test simulation conducted by the present inventors. In a two-cell, one-cooled fuel cell, there are refrigerant channels only on one side of each of the cathode side and the anode side. As a result, if the internal configuration of the 2-cell 1-cooled fuel cell is the same (specifically, the hydrogen and air gas flow paths have the same shape and cross-sectional area), FIG. As shown in FIG. In FIG. 2, Normal indicates the characteristics of a one-cell, one-cooled fuel cell (that is, a configuration in which one refrigerant channel is provided between each MEA). Left corresponds to the characteristics of the cell in which the anode is cooled in the 2-cell 1-cooled configuration, and Right corresponds to the characteristics of the cell in which the cathode is cooled in the 2-cell 1-cooled configuration. In the Right cell in which only the cathode side is cooled, the voltage drop starts from around 62 ° C. On the other hand, in the Left cell in which only the anode side is cooled, the voltage is kept high up to around 67 ° C.

  FIG. 3 shows the relationship between the anode gas flow rate and the cell voltage at a cell temperature of 66 ° C. As a result of examining the correlation between the anode gas flow rate and the cell voltage, as shown in FIG. 3, the Right cell (broken line) and the Left cell (solid line) show different characteristics. As can be seen from FIG. 3, the voltage of the Left cell decreases as the stoichiometry increases (the more hydrogen gas flows). On the other hand, the voltage of the Right cell decreases as the stoichiometry of hydrogen gas decreases (the more hydrogen gas flows). In other words, in order to improve the performance of both cells, the left cell stoichiometry may be lowered and the right cell stoichiometry may be raised. This tendency is reflected in the configuration of the fuel cell of the first embodiment.

In the first embodiment described above, the MEA (that is, the solid polymer electrolyte membrane 12 and the electrode catalyst layers 14 and 20) of the left unit cell 10 is the “first membrane electrode assembly” in the first invention. In addition, the MEA of the right unit cell 110 (that is, the solid polymer electrolyte membrane 112 and the electrode catalyst layers 114 and 120) is the “second membrane electrode assembly” in the first invention, and the intermediate separator 306 is the In the “intermediate separator” in the first invention, the separator 304 is in the “outer separator” in the first invention, and the cooling liquid channels 300 and 312 are in the “refrigerant channel” in the first invention. It corresponds. Then, in the first embodiment, the凹深of D ₁ of the separator 304, configured to shallower than凹深of D ₂ of the intermediate separator 306, the concave of the flow path of "the outer separator in the first aspect of the present invention The relationship that the cross-sectional area <the cross-sectional area of the concave channel on the second membrane electrode assembly side of the intermediate separator ”is established.

In Embodiment 1, the ratio of D ₁ : D ₂ = 1.0: 1.1 is used, but the present invention is not limited to this. According to the knowledge of the present inventor, it is considered that the difference may be increased up to about D ₁ : D ₂ = 1.0: 1.2. In terms of the flow rate ratio, it is considered that a difference of about 1.1 to 1.3 times should be obtained. The separators 304 and 306 both have a trapezoidal concave cross-sectional shape, but the concave cross-sectional shape may be asymmetrical with the separators 304 and 306. By making the cross-sectional area and cross-sectional shape different, the pressure loss and thus the flow rate can be made different.

Embodiment 2. FIG.
FIG. 4 is an exploded perspective view showing the configuration of the fuel cell of the second embodiment. The same components as those in FIG. 1 are denoted by the same reference numerals. In this perspective view, each separator has a rectangular through hole. By connecting these through holes in the unit cell stacking direction, manifolds for hydrogen, air, and coolant are formed.

  In the second embodiment, the pressure at the anode hydrogen manifold inlet / outlet portion of the left unit cell 10 is higher than the pressure loss at the anode hydrogen manifold inlet / outlet portion of the right unit cell 110, so that Change the size of the gas flow path on the side. That is, the opening cross-sectional area of the joining portion 305 between the manifold and the recess (gas flow path 18) in the separator 304 is smaller than the opening cross-sectional area of the joining portion 307 between the manifold and the recess (the gas flow path 118) in the separator 306. (Narrow). Thereby, similarly to Embodiment 1, the gas flow path 18 has a relatively small gas flow rate, and the gas flow path 118 has a relatively high gas flow rate. As a result, the flow rate of hydrogen at the anode of the right unit cell 110 can be relatively increased as compared with the left unit cell 10 by a method different from that of the first embodiment.

Note that the opening cross-sectional area can be made different by changing any of the depth, width, and shape of the merging portions 305 and 307. In addition, the merging portion 305 may be narrowed entirely or partially so that the gas flow rate of the merging portion 305 is reduced more than the gas flow rate of the merging portion 307. Moreover, it is good also considering only either one among the merge part on the exit side of the manifold and the merge part on the inlet side. Although the second embodiment also includes the separator configuration (D ₁ <D ₂ ) of the _first embodiment, the present invention is not limited to this. That is, for the fuel cell having the same cross-sectional area and the same cross-sectional shape in the gas flow path of the anode and cathode of each unit cell (that is, for the fuel cell having the same cross-sectional shape of the unevenness of the separator) The manifold inlet / outlet configuration may be applied. Also in this case, the flow rate of hydrogen in the anode of one of the two cells and one cooling type cell can be relatively increased.

  In the second embodiment described above, the configuration in which the opening cross-sectional area of the merging portion 305 is made narrower than the opening cross-sectional area of the merging portion 307 is “the flow path disconnection of the merging portion of the outer separator” in the first invention. The relationship of “area <flow path cross-sectional area of the merging portion on the second membrane electrode assembly side of the intermediate separator” is established.

Embodiment 3 FIG.
FIG. 5 shows a configuration of a fuel cell according to Embodiment 3 of the present invention. In the third embodiment, as shown in FIG. 5, the concave width relationship is W ₁ <W ₂ , specifically, the ratio of the width W ₁ to the width W ₂ is W ₁ : W ₂ = 1.0: 1. Set to 1. As a result, the hydrogen flow rate in the gas flow path 118 is increased as compared with the hydrogen flow rate in the gas flow path 18 as in the case of D ₁ : D ₂ = 1.0: 1.1 in the _first embodiment. be able to. The ratio of the width W ₁ and the width W ₂ of the above is an example, it can be applied similarly to various ratios of as described in the first embodiment.

Embodiment 4 FIG.
It should be noted that a function similar to that of the first to third embodiments, that is, a function of changing the flow rate or the like, may be realized by changing (differentiating) the number of grooves.

10 Left unit cell 110 Right unit cell 12, 112 Solid polymer electrolyte membrane 14, 20, 114, 120 Electrocatalyst layer 16, 22, 116, 122 Gas diffusion layer 18, 24, 118, 124 Gas flow path 300, 312 Cooling Liquid channel 306 Intermediate separators 302, 304, 308, 310 Separator 305, 307

Claims (1)

A first membrane electrode assembly comprising: an electrolyte membrane; an anode electrode catalyst layer provided on one surface of the electrolyte membrane; and a cathode electrode catalyst layer provided on the other surface of the electrolyte membrane;
An electrolyte membrane disposed on the cathode electrode catalyst layer side of the first membrane electrode assembly, an anode electrode catalyst layer provided on a surface of the electrolyte membrane on the first membrane electrode assembly side, and the electrolyte membrane A cathode electrode catalyst layer provided on the other surface of the second membrane electrode assembly,
A plurality of recesses interposed between the first and second membrane electrode assemblies, and a merging portion where the plurality of recesses merge are provided on the respective surfaces of the first and second membrane electrode assemblies. An intermediate separator provided,
The first membrane electrode assembly is disposed on the anode catalyst layer side, and a plurality of recesses and a junction where the plurality of recesses merge together are connected to the anode catalyst layer side on the first membrane electrode assembly side. An outer separator provided on the facing surface;
A coolant channel positioned so as to sandwich the first membrane electrode assembly, the intermediate separator, and the second membrane electrode assembly;
With
The concave channel total cross-sectional area of the outer separator <the concave channel total cross-sectional area of the intermediate separator on the second membrane electrode assembly side; and
A configuration in which the flow path cross-sectional area of the merging portion of the outer separator <the flow channel cross-sectional area of the merging portion on the second membrane electrode assembly side of the intermediate separator;
A fuel cell comprising at least one of the configurations.

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