JP2007122898A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and conductive fuel cell by improving a separator. <P>SOLUTION: The fuel cell comprises an anode separator 4 and a cathode separator 5; and an anode separator 20 and a cathode separator 21 where tops 32, 35 of plates 20a, 21a are higher than the tops of the anode separator 4 and the cathode separator 5. The fuel cell is composed by laminating a unit cell having the anode separator 4 and the cathode separator 5, and a unit cell having the anode separator 20 and the cathode separator 21. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell.

  Generally, a polymer electrolyte fuel cell stack has a pair of separators each provided with a flow path for a fuel gas and an oxidant gas on the surface, and a membrane electrode joint provided with a gas diffusion layer (hereinafter referred to as GDL) on both sides. It is configured by laminating a plurality of unit cells consisting of a body (hereinafter referred to as MEA). At this time, the GDL is compressed by a certain amount by a laminating load to generate a surface pressure between the separator and the GDL. The electrical conductivity between the separator is secured. On the other hand, if GDL is compressed excessively, gas diffusibility is hindered and power generation performance is reduced. Therefore, the compression amount must be within a predetermined range.

  However, since carbon paper and carbon cloth that are generally used as GDL have a large thickness variation with respect to the compression amount, they are necessary even when the lower limit of the thickness variation, that is, when the thickness is smaller than the set thickness. When the height of each part of the MEA and the separator is determined so that the compression amount can be secured, the upper limit of the thickness variation, that is, when the thickness is thicker than the set thickness, the gap between the MEA and the separator is expanded at the cell outer periphery, and the cell There is a problem in that the crushing margin of the seal provided on the outer peripheral portion is reduced and the sealing performance is lowered.

  For this reason, conventionally, in order to ensure sufficient sealing performance even at the upper limit of the thickness variation of the GDL, a large allowance is provided for the allowance for crushing the seal.

Further, Patent Document 1 discloses a method of reducing the thickness of a unit cell by using a metal separator and reducing the size of the fuel cell stack.
JP 2004-227894 A

  However, in order to ensure sufficient sealing performance even at the upper limit of GDL thickness variation, it is necessary to secure the height of the seal by that amount in order to provide a margin for the collapse of the seal. However, if the seal height is sufficiently secured, the height of the entire cell is determined by the height of the seal portion, so the pitch between cells cannot be reduced beyond a certain level, resulting in a smaller fuel cell stack. Is limited.

  In addition, when a metal separator is used, the rigidity of the separator is relatively low. Therefore, when the collapse amount of the seal is reduced, the deformation of the separator corresponding to the decrease in the collapse amount is accumulated in a certain unit cell. There is a problem that the amount of deformation of the unit cell becomes large and a seal failure is likely to occur.

  The present invention was invented to solve such problems, and an object thereof is to obtain a fuel cell having a small size, good sealing properties, and good conductivity.

  In the present invention, the electrolyte membrane, the gas diffusion layer sandwiching the electrolyte membrane and diffusing the fuel gas or the oxidant gas, the gas flow path on the surface facing the gas diffusion layer, and contacting the gas diffusion layer to gas In a fuel cell in which unit cells including a contact portion that compresses a diffusion layer and a seal portion that prevents leakage of fuel gas or oxidant gas are stacked, the separator includes the first separator and A second separator in which the height of the contact portion in the unit cell stacking direction is higher than the height of the contact portion of the first separator, and the first unit cell having the first separator, A second unit cell having two separators is stacked in combination.

  In addition, an electrolyte membrane, a gas diffusion layer sandwiching the electrolyte membrane and diffusing fuel gas or oxidant gas, a gas flow path on a surface facing the gas diffusion layer, and in contact with the gas diffusion layer, the gas diffusion layer In a method for assembling a fuel cell in which unit cells are provided, the separator includes a contact portion that compresses the fuel cell and a seal portion that prevents leakage of fuel gas or oxidant gas. And a second separator in which the height of the contact portion in the unit cell stacking direction is higher than the height of the contact portion of the first separator. And the process which laminates | stacks the 1st unit cell which has a 1st separator and provides a load, the compression amount detection process which detects the compression amount of a gas diffusion layer after providing a load, and a compression amount from predetermined value And the step of laminating the second unit cell having the second separator is repeated.

  According to the present invention, the first separator, the second separator having a contact portion higher than the first separator, the first unit cell having the first separator, and the second separator having the second separator are provided. By stacking the unit cells, it is possible to absorb variations in the amount of compression, prevent gas leakage at the seal portion, reduce the height of the seal portion, and reduce the size of the fuel cell. A decrease in contact surface pressure with the first separator can be suppressed, and a decrease in conductivity can be suppressed.

  A fuel cell according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic view showing a part of the fuel cell of this embodiment. In this embodiment, an anode separator and a cathode separator between adjacent unit cells will be described later in detail, and are composed of anode separators (separators) 4 and 20 and cathode separators (separators) 5 and 21. FIG. 2 is a schematic configuration diagram centering on a portion (hereinafter referred to as A part) having an anode separator (first separator) 4 and a cathode separator (first separator) 5 in FIG. 1, and FIG. 1 is a schematic configuration diagram centering on a portion (hereinafter, referred to as B portion) having an anode separator (second separator) 20 and a cathode separator (second separator) 21 in FIG.

  Here, the unit cell constituting the fuel cell will be described with reference to FIG. Here, a description will be given using a unit cell having an A portion. In FIG. 2, a gap is provided between the gas diffusion layer and the anode separator 4 and the cathode separator 5 for explanation.

  The unit cell includes a polymer electrolyte membrane (hereinafter referred to as an electrolyte membrane) 1, a gas diffusion layer (hereinafter referred to as GDL) 2 provided on both main surfaces of the electrolyte membrane 1 serving as a power generation reaction surface of the unit cell, A resin plate 3 provided on both main surfaces of the electrolyte membrane 1 not provided with GDL2, an anode separator 4 having a hydrogen flow path 10 for supplying hydrogen to one GDL2, and an air flow for supplying air to the other GDL2 A cathode separator 5 having a passage 14.

  The electrolyte membrane 1 is made of, for example, Nafion (registered trademark).

  The GDL 2 is made of, for example, carbon paper, and includes a catalyst layer (not shown) having a catalyst such as platinum on the side in contact with the electrolyte membrane 1. In the following, the region where the GDL 2 is provided is referred to as a power generation reaction region 18.

  The resin plate 3 sandwiches the electrolyte membrane 1 outside the power generation reaction region 18 and is made of a resin having higher rigidity than the GDL 2.

  The anode separator 4 includes a metal plate 4a and an anode frame 6 connected to the plate 4a.

  The plate 4a has a cross-sectional shape of a surface facing the power generation reaction region 18, for example, a corrugated shape, and a hydrogen flow path (gas flow path) 10 through which hydrogen flows is formed. In addition, a cooling water channel 11 a for cooling the unit cell is formed on the back surface of the hydrogen channel 10. The plate 4 a comes into contact with the GDL 2 by the top portion (contact portion) 12, and comes into contact with the back surface of the groove bottom 16 of the air flow channel 14 of the adjacent cathode separator 5 by the back surface of the groove bottom 13 of the hydrogen flow channel 10.

  The anode frame 6 is in contact with the resin plate 3 and includes a groove 6a provided on a part of the surface facing the resin plate 3, and a groove 6b provided on the back side of the groove 6a. A lip seal 8 is provided in the groove 6a (the anode frame 6 and the lip seal 8 constitute a seal portion). The lip seal 8 is loaded, brought into contact with the resin plate 3 and compressed when the unit cell is laminated to form a fuel cell, so that the anode frame 6 and the resin plate 3 are in close contact with each other. To prevent leakage outside the unit cell. Further, a liquid sealing agent 9 is provided in the groove 6b. The liquid sealing agent 9 is in intimate contact between the groove 6b and the groove 7b provided in the cathode frame 7 of the adjacent unit cell to prevent leakage of cooling water.

  The cathode separator 5 includes a metal plate 5a and a cathode frame 7 connected to the plate 5a.

  The plate 5a has a cross-sectional shape that faces the power generation reaction region 18, for example, a corrugated shape, and an air flow path (gas flow path) 14 through which air flows is formed. In addition, a cooling water channel 11b for cooling the unit cell is formed on the back surface of the air channel 14. The plate 5 a comes into contact with the GDL 2 by the top portion (contact portion) 15, and the back face of the groove bottom 16 of the air flow path 14 comes into contact with the back face of the groove bottom 13 of the hydrogen flow path 10 of the adjacent anode separator 4.

  The cathode frame 7 is provided with a groove portion 7a provided in a part of a surface which contacts the resin plate 3 and faces the resin plate 3, and a groove portion 7b provided on the back side of the groove portion 7a. The groove portion 7a is provided with a lip seal 8 (the cathode frame 7 and the lip seal 8 constitute a seal portion). The lip seal 8 is loaded, brought into contact with the resin plate 3 and compressed when the unit cell is laminated to form a fuel cell, so that the cathode frame 7 and the resin plate 3 are in close contact with each other. To prevent leakage outside the unit cell. Moreover, the liquid sealing agent 9 is provided in the groove part 7b.

  The plate 4 a and the plate 5 a are welded on the back surfaces of the groove bottom 13 and the groove bottom 16. Thereby, the electrical conductivity between the anode separator 4 and the cathode separator 5 can be improved. The welding may be performed by brazing or diffusion bonding.

  A unit cell is configured by the above configuration. In this embodiment, part A is constituted by an anode separator 4 of a certain unit cell and a cathode separator 5 of a unit cell adjacent to the certain unit cell.

  Next, part B will be described with reference to FIG. In the part B, the shape of the anode separator 20 and the cathode separator 21 before assembly is the same as the shape of the anode separator 4 and the cathode separator 5 provided in the part A, but between the anode separator 20 and the cathode separator 21. The difference is that the intermediate plate 22 is provided.

  The anode separator 20 includes a metal plate 20a and an anode frame 6 connected to the plate 20a.

  The plate 20a has a cross-sectional shape of the surface facing the power generation reaction region 18, for example, a corrugated shape, and a hydrogen flow path (gas flow path) 30 through which hydrogen flows is formed. Further, a cooling water channel 31 a for cooling the unit cell is formed on the back surface of the hydrogen channel 30. The plate 20 a comes into contact with the GDL 2 through the top portion (contact portion) 32, and comes into contact with the intermediate plate 22 through the back surface of the groove bottom 33 of the hydrogen flow path 30.

  The cathode separator 21 includes a metal plate 21a and a cathode frame 7 connected to the plate 21a.

  The plate 21a has a cross-sectional shape that faces the power generation reaction region 18 in a corrugated shape, for example, and an air flow path (gas flow path) 34 through which air flows is formed. In addition, a cooling water flow path 31 b for cooling the unit cell is formed on the back surface of the air flow path 34. The plate 20 b comes into contact with the GDL 2 through the top portion (contact portion) 35 and comes into contact with the intermediate plate 22 through the back surface of the groove bottom 36 of the air flow path 34.

  The intermediate plate 22 includes a plurality of through holes 23 in order to reduce the pressure loss of the cooling water flowing through the cooling water channel 31a of the anode separator 20 and the cooling water channel 31b of the cathode separator 31. The surface of the intermediate plate 22 is preferably subjected to a conductive surface treatment.

  The plate 20 a, the plate 21 a, and the intermediate plate 22 are welded on the back surface of the groove bottom 33 of the hydrogen flow path 30 and the back surface of the groove bottom 36 of the air flow path 34. As a result, the positions of the anode separator 20, the cathode separator 21, and the intermediate plate 22 can be fixed, and the conductivity can be improved.

  Other configurations are the same as those described with reference to FIG. In FIG. 3, the same components as those described with reference to FIG. 2 are denoted by the same reference numerals as those in FIG. 2, and description thereof is omitted here.

  In part A having the anode separator 4 and the cathode separator 5 in this embodiment, the height of the anode frame 6 and the cathode frame 7 in the stacking direction of the unit cells is T1, and the height of the plate 4a and the plate 5a, that is, The height from the top 12 of the anode separator 4 to the top 15 of the cathode separator 5 is T2.

  On the other hand, in the B part having the anode separator 20 and the cathode separator 21, the height of the anode frame 6 and the cathode frame 7 is set to T1 as in the A part, and the height of the plate 20a and the plate 21a, that is, the anode separator 20 The height from the top 32 to the top 35 of the cathode separator 21 is defined as T2 ′.

  In this embodiment, in the part A, the difference between the height T1 and the height T2 is compressed to the upper limit value of the manufacturing variation of the thickness in the GDL2, that is, the maximum dimension GDL2, and the gas diffusibility is sufficiently maintained. Double the size. In other words, when GDL2 is compressed by the top portions 12 and 15 so that the difference in height between the anode frame 6 or the cathode frame 7 and the anode separator 4a or the cathode separator 5a becomes the upper limit of manufacturing variation, a predetermined gas diffusion is performed in the GDL2. The difference in height that retains the sex. Thereby, when the GDL 2 is compressed by the top portion 12 of the anode separator 4 or the top portion 15 of the cathode separator 5, the gas diffusibility of the GDL 2 can be sufficiently secured, and the anode frame can be obtained regardless of the manufacturing variation of the GDL 2 thickness. 6 and the cathode frame 7 are in contact with the resin plate 3 and the lip seal 8 is compressed, so that the crushing allowance of the lip seal 8 does not decrease. Therefore, it is not necessary to increase the crushing margin of the lip seal 8, and the height of the lip seal 8 can be reduced. That is, the fuel cell can be reduced in size.

  However, in a laminate in which unit cells (first unit cells) having only part A are stacked, if there is GDL2 whose GDL2 thickness is near the lower limit of manufacturing variation, the amount of compression of GDL2 decreases, and anode separator 4 Alternatively, the contact pressure between the cathode separator 5 and the GDL 2 may decrease, and the conductivity may decrease.

  Therefore, in this embodiment, the intermediate plate 22 is provided, and the unit cell (the first cell) having the B portion in which the difference between the height T1 and the height T2 ′ is smaller than the difference between the height T1 and the height T2 in the A portion. 2 unit cells) are stacked on a part of the fuel cell.

  When the unit cells having the A part are laminated and given a predetermined load, the compression amount of the GDL2 of the laminated unit cells is detected, and the integrated value of the shortage of the compression amount is half the thickness of the intermediate plate 22, The unit cells having the B part are stacked. That is, when the integrated value of the insufficient amount of compression of GDL2 is half the thickness of the intermediate plate 22 that is the difference in height between the A part and the B part, the unit cells having the B part are stacked. Thereafter, the unit cell having the A portion is again laminated. In the B part, the contact resistance between the anode separator 4 and the cathode separator 5 and the GDL 2 is smaller than a preset predetermined resistance value, and the gas diffusivity of the GDL 2 is larger than a preset predetermined amount. Laminate. As a result, even when the A part having GDL2 whose manufacturing variation is near the lower limit is laminated, it is possible to prevent the GDL2 from being compressed and to suppress the decrease in conductivity between the anode separator 4 or the cathode separator 5 and the GDL2. it can.

  Note that the compression amount of GDL2 is calculated, for example, by detecting the height or reaction force when stacking unit cells and applying a load, and based on the value.

  The effect of 1st Embodiment of this invention is demonstrated.

  In this embodiment, the unit cell having an A portion where the height of the top portion 12 of the plate 4a and the top portion 15 of the plate 5a contacting the GDL 2 is T2, and the height of the top portion 32 of the plate 20a and the top portion 42 of the plate 21a. A fuel cell is configured by stacking unit cells having a B portion with a length of T2 ′ (T2 <T2 ′).

  In part A, when GDL2 is used in which the difference between the heights T1 and T2 of the anode frame 6 connected to the plate 4a and the cathode frame 7 connected to the plate 5a is the upper limit value of manufacturing variation, gas diffusibility is used. Is twice the dimension that can be sufficiently obtained. By laminating the unit cells having the A part, the anode frame 6 and the cathode frame 7 are in contact with the resin plate 3 while maintaining the gas diffusibility of the GDL 2 regardless of the manufacturing variation of the GDL 2, and the lip seal 8 Since it is compressed, the crushing margin of the lip seal 8 does not decrease. Therefore, the height of the lip seal 8 can be reduced, and the fuel cell can be reduced in size.

  In the portion B, the difference between the heights T1 and T2 'of the anode frame 6 connected to the plate 20a and the cathode frame 7 connected to the plate 21a is made smaller than that in the portion A. Then, the unit cells having the A part are stacked, and the unit cell having the B part is stacked when the GDL2 compression amount shortage is half the thickness of the intermediate plate 22 sandwiched between the anode separator 20 and the cathode separator 21. . When GDL2 whose manufacturing variation of GDL2 is not the upper limit is laminated and the contact surface pressure between anode separator 4 or cathode separator 5 and GDL2 is reduced, unit cells having part B are laminated to form anode separator 4 The top 12 or the top 15 of the cathode separator 5 and the GDL 2 can be prevented from decreasing in conductivity due to a decrease in contact surface pressure, and an increase in contact resistance can be prevented.

  In the part B, the intermediate plate 22, the anode separator 20, and the cathode separator 21 can be fixed by sandwiching and welding the intermediate plate 22 between the anode separator 20 and the cathode separator 21. As a result, it is possible to prevent displacement between the intermediate plate 22, the anode separator 20, and the cathode separator 21, and to reduce the contact resistance.

  In addition, the pressure loss can be reduced by providing the through hole 23 at a location of the intermediate plate 22 facing the cooling water flow paths 31a and 31b.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a schematic view showing a part of the fuel cell of this embodiment. In this embodiment, in addition to the part A of the first embodiment, the fuel cell includes separators 40 and 50 that do not have a cooling water flow path. The separator (first separator) 40 will be described with reference to FIG. 5, and the separator (second separator) 50 will be described with reference to FIG.

  The separator 40 includes a metal plate 40a and a frame 45 connected to the plate 40a.

  The plate 40a has a cross-sectional shape, for example, a corrugated shape, a hydrogen channel (gas channel) 41 through which hydrogen flows is formed on one surface, and an air channel (gas flow) through which air flows on the other surface. Road) 42 is formed. The separator 40 is brought into contact with the GDL 2 by the top (contact part) 43 of the hydrogen channel 41 and the top (contact part) 44 of the air channel 42.

  The frame 45 includes groove portions 45 a and 45 b provided in a part of the surface facing the resin plate 3. A lip seal 8 is provided in the groove portions 45a and 45b (the frame 45 and the lip seal 8 constitute a seal portion).

  The separator 50 includes a metal plate 50a and a frame 45 connected to the plate 50a.

  The plate 50a has a cross-sectional shape, for example, a corrugated shape. A hydrogen channel (gas channel) 51 through which hydrogen flows is formed on one surface, and an air channel (gas flow) through which air flows on the other surface. Road) 52 is formed. The separator 50 is brought into contact with the GDL 2 through the top (contact portion, second contact portion) 53 of the hydrogen flow channel 51 and the top (contact portion, second contact portion) 54 of the air flow path 52.

  In the separator 40 and the separator 50, the height T3 between the top 43 and the top 44 is different from the height T4 between the top 53 and the top 54, and the height T4 is higher than the height T3. . That is, the difference between the height T5 and the height T4 is smaller than the difference between the height T5 and the height T3 of the frame 45. In this embodiment, the difference between the height T1 and the height T2 of the A portion is equal to the difference between the height T5 and the height T3 of the separator 40.

  In this embodiment, a unit cell (first unit cell) having a part A and a separator 40 is stacked to form a stacked body, and the integrated value of the insufficient amount of compression of GDL2 is the height T4 and the height. When the difference from T3 is half, the unit cell (second unit cell) having the separator 50 is stacked instead of the separator 40. Thereafter, the unit cell having the A part and the separator 40 is again laminated.

  The effect of 2nd Embodiment of this invention is demonstrated.

  In this embodiment, a unit cell including a separator 40 having a height of the top portion 43 and the top portion 44 of T3 and a separator 50 having a height of the top portion 53 and the top portion 54 of T4, and having a portion A, The unit cell having the separator 40 is stacked, and when the GDL2 compression amount short reaches half of the difference between the height T4 and the height T3, the unit cell having the separator 50 is stacked instead of the separator 40. . As a result, the same effect as in the first embodiment can be obtained.

  It goes without saying that the present invention is not limited to the above-described embodiments, and includes various modifications and improvements that can be made within the scope of the technical idea.

  It can be used for fuel cell vehicles.

It is a schematic block diagram which shows a part of fuel cell of 1st Embodiment of this invention. It is a schematic block diagram of the A section of 1st Embodiment of this invention. It is a schematic block diagram of the B section of 1st Embodiment of this invention. It is a schematic block diagram which shows a part of fuel cell of 2nd Embodiment of this invention. It is a schematic block diagram of the separator of 2nd Embodiment of this invention. It is a schematic block diagram of the separator of 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolyte membrane 2 Gas diffusion layer 3 Resin plate 4 Anode separator (separator, 1st separator)
5 Cathode separator (separator, first separator)
6 Anode frame 7 Cathode frame 8 Lip seal 10, 30, 41, 51 Hydrogen flow path (gas flow path)
14, 34, 42, 52 Air channel (gas channel)
12, 15, 43, 44 Top (contact part)
20 Anode separator (separator, second separator)
21 Cathode separator (separator, second separator)
22 Intermediate plate 23 Through hole 32, 35, 53, 54 Top (contact portion)

Claims (8)

An electrolyte membrane;
A gas diffusion layer for sandwiching the electrolyte membrane and diffusing fuel gas or oxidant gas;
A gas flow path on a surface facing the gas diffusion layer, a contact portion that contacts the gas diffusion layer and compresses the gas diffusion layer, and a seal portion that prevents leakage of the fuel gas or the oxidant gas And a separator having a unit cell comprising:
The separator is
A first separator;
The height of the contact portion in the unit cell stacking direction is a second separator higher than the height of the contact portion of the first separator, and
A first unit cell having the first separator;
A fuel cell, wherein the second unit cell having the second separator is stacked in combination.   2. The fuel cell according to claim 1, wherein the second separator is composed of a pair of an anode separator and a cathode separator, and has an intermediate plate therebetween.   The fuel cell according to claim 2, wherein the intermediate plate is subjected to a conductive surface treatment.   4. The fuel cell according to claim 2, wherein each of the separators is composed of a pair of an anode separator and a cathode separator, and a cooling water flow path is provided therebetween.   The fuel cell according to claim 4, wherein the intermediate plate has a through hole at a location facing the groove bottom of the cooling water passage.   6. The fuel cell according to claim 2, wherein the second separator and the intermediate plate are welded. An electrolyte membrane;
A gas diffusion layer for sandwiching the electrolyte membrane and diffusing fuel gas or oxidant gas;
A gas flow path on a surface facing the gas diffusion layer, a contact portion that contacts the gas diffusion layer and compresses the gas diffusion layer, and a seal portion that prevents leakage of the fuel gas or the oxidant gas In a method for assembling a fuel cell in which unit cells having a separator are stacked,
The separator is
A first separator;
The height of the contact portion in the unit cell stacking direction is a second separator higher than the height of the contact portion of the first separator, and
Laminating the first unit cell having the first separator and applying a load;
A compression amount detecting step of detecting a compression amount of the gas diffusion layer after applying the load;
And a step of stacking the second unit cells having the second separator when the compression amount does not satisfy a predetermined condition.   The predetermined condition is a condition that a contact resistance between the first contact portion and the gas diffusion layer is smaller than a predetermined resistance value, and a gas diffusion of the gas diffusion layer is larger than a predetermined amount. 8. The fuel cell assembling method according to claim 7, wherein the fuel cell is assembled.