JP2005285350A - Polymer electrolyte fuel cell - Google Patents

Abstract

An object of the present invention is to provide a polymer electrolyte fuel cell that has a highly reliable assembly property and has excellent sealing properties and stable output characteristics during battery operation.
A polymer electrolyte fuel cell according to the present invention includes a water absorbing material made of a substance that swells due to water absorption in a gap formed between an electrode and a seal member. At the time of assembly, the clearance between the seal member and the electrode can be sufficiently secured, so that the assembly becomes easy. Further, when the assembled fuel cell is in operation, the water absorbing material in the gap absorbs water in the reaction gas supplied and / or water generated by an electrochemical reaction in the electrode portion, and swells. Therefore, the outflow of gas to the gap can be suppressed.
[Selection] Figure 7

Description

  The present invention relates to a polymer electrolyte fuel cell used for a portable power source, a power source for portable devices, a power source for electric vehicles, a domestic cogeneration system, and the like.

  A fuel cell using a polymer electrolyte membrane generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air. This fuel cell includes a polymer electrolyte membrane that selectively transports hydrogen ions, and a pair of electrodes formed on both sides of the polymer electrolyte membrane, that is, an anode and a cathode. This is called MEA (electrolyte membrane / electrode assembly). The electrode is mainly composed of carbon powder supporting a platinum group metal catalyst, and has both a catalyst layer formed on both surfaces of the polymer electrolyte membrane and an air permeability and electronic conductivity formed on the outer surface of the catalyst layer. It consists of a gas diffusion layer.

Next, in order to prevent the supplied fuel gas and oxidant gas from leaking out or mixing the two kinds of gases with each other, a sealing material such as a gasket is sandwiched around the polymer electrolyte membrane. Is placed. This sealing material is integrated with the electrode and the polymer electrolyte membrane in advance. Usually, this is also called MEA, but the one containing the sealing material is sometimes called MESA (electrolyte membrane / electrode / sealing material assembly).
Outside the MEA, a conductive separator plate that mechanically fixes the MEA and electrically connects adjacent MEAs to each other in series is disposed. The separator plate has a gas flow path for supplying reaction gas to the electrode surface and carrying away generated gas and surplus gas. Although the gas flow path can be provided separately from the separator plate, a method of providing a gas flow path by providing a groove on the surface of the separator plate is generally used.

  In order to supply the reaction gas to the groove of the separator plate, a piping jig that branches the piping for supplying the reaction gas to the number of separator plates to be used and directly connects the branch destination to the groove on the separator plate is required. Become. This jig is called a manifold, and the type that connects directly from the reaction gas supply pipe as described above is called an external manifold. In addition, there is a type of this manifold called an internal manifold with a simplified structure. The internal manifold is a separator plate in which a gas flow path is formed with a through-hole, the gas flow path is connected to this hole, and the reaction gas is supplied directly from the hole.

  Since the fuel cell generates heat during operation, it is necessary to cool it with cooling water or the like in order to maintain the battery in a favorable temperature state. Usually, a cooling part is provided for every 1 to 3 cells. In many cases, a cooling water flow path is provided on the back surface of the separator plate to form a cooling section. These MEAs and separator plates are alternately stacked, and after stacking 10 to 200 cells, the stacked body is sandwiched between end plates via current collector plates and insulating plates, and is generally fixed from both ends with fastening bolts. This is a typical stacked battery structure.

Such a polymer electrolyte fuel cell sealing material is required to have high dimensional accuracy, sufficient elasticity, and sufficient fastening allowance in order to perform gas sealing while making contact between the separator plate and the electrode. The For this reason, a sheet-like gasket made of resin, rubber, or the like, or an O-ring gasket made of rubber has been conventionally used as a sealing material.
Recently, as described in Patent Documents 1 and 2, for example, the load required for sealing the gasket is reduced in order to reduce the weight of the structural member by reducing the stack fastening load, simplify the structure, and reduce the cost. Has been tried. Further, the cross-sectional shape of the gasket has been attempted not only in the O-ring shape but also in a triangular shape or a semicircular shape.

  For gaskets having a certain cross-sectional area such as an O-ring, it has been attempted to configure the gasket on the separator plate side. When the gasket is an O-ring, sealing is performed by pressing the electrolyte membrane against the separator plate with the gasket. Therefore, the gas seal configuration requires two locations, the anode side gas seal and the cathode side gas seal, and there is a problem that the part necessary for the sealing is enlarged. Furthermore, it is necessary to provide the separator plate with a groove to be filled with the O-ring type gasket, and there is a restriction that the thickness of the separator plate cannot be reduced in order to ensure the groove size. In order to solve such problems, attempts have been made to save the space of the sealing material.

Generally, sealing is performed by sandwiching an electrolyte membrane with an O-ring or flat gasket as a sealing material.
When the sealing material is an O-ring gasket, it is necessary to provide a groove for the O-ring to fill the separator plate, and there is a restriction that the thickness of the separator plate cannot be reduced in order to ensure the groove dimension. This causes an increase in the volume of the laminated battery, an increase in cost, and a complicated separator plate shape, resulting in a deterioration in yield during the processing of the separator plate.

  Further, when assembling the laminated battery, the MEA is arranged on the separator plate, and further, the separator plate or the O-ring gasket and the separator plate are arranged thereon. This process is repeated to form a battery stack. At that time, the O-ring gasket or separator plate arranged on the MEA is assembled using a guide of an assembling jig. However, each part has a dimensional error. From the viewpoint of assembling between the electrode and the O-ring gasket or the separator plate, between the O-ring gasket and the electrode, to ensure workability or manufacturing yield. Clearance is required.

When this clearance is small, the reliability at the time of assembly becomes low. For example, a seal failure occurs when a part of the electrode bites into the O-ring gasket. Further, when the O-ring-shaped gasket hits the electrode, an excessive surface pressure is generated on the electrode, and the battery performance is deteriorated due to breakage of the electrolyte membrane or deterioration of durability.
Therefore, when the clearance between the O-ring gasket and the electrode is made small, it is necessary to improve the accuracy of the component dimensions, leading to a decrease in yield and an increase in component cost. In particular, in the molded separator plate, there is a limit to the processing accuracy of the guide portion used at the time of assembly, and it is difficult to reduce the clearance between the O-ring gasket and the electrode. For this reason, after the separator plate is formed, the guide portion must be added by post-processing, and the cost increases accordingly.

On the other hand, if the clearance between the O-ring-shaped gasket and the electrode is increased in order to secure the assemblability, the reaction gas flows into the clearance. Therefore, there is a possibility that the reaction gas does not flow in the gas flow path of the separator plate. Further, if the clearance for each single cell varies due to an assembly error between the MEA and the O-ring gasket, the pressure loss between the single cells also varies. At this time, since the reaction gas corresponding to the pressure loss of each single cell flows in each single cell in the laminated battery, the flow rate of the reaction gas varies. For this reason, the battery performance varies between the single cells, which causes adverse effects such as a decrease in power generation voltage, a decrease in durability, or a decrease in stability during low-power operation. These symptoms are remarkable on the fuel gas side where the utilization rate of the reaction gas is relatively large.
JP-A-11-233128 JP 2002-141082 A

  The present invention has a reliable assembling property when assembling the laminated battery, and reduces the clearance between the seal member and the electrode during the operation of the laminated battery, thereby providing excellent sealing performance and stable output characteristics. An object of the present invention is to provide a polymer electrolyte fuel cell.

  In order to solve the above problems, a polymer electrolyte fuel cell according to the present invention includes a hydrogen ion conductive polymer electrolyte membrane, a pair of electrodes disposed on both sides of the polymer electrolyte membrane, and a reactive gas supplied to the electrodes. A pair of conductive separator plates having a gas flow path, and a pair of seal members that keep the electrodes and the conductive separator plates airtight, and at least a part of a gap formed between the electrodes and the seal members And a water-absorbing material made of a substance that swells due to water absorption.

  According to the present invention, the water absorbing material provided in the gap formed between the electrode and the seal member absorbs the reaction gas supplied during battery operation and / or moisture generated by the reaction and swells. Therefore, even if the gap between the electrode and the seal member is set so as not to hinder the assembly of the battery, the gas can be prevented from flowing into the gap due to the expanded water absorbing material when the battery is operating. For this reason, not only can a gas seal be secured, but also a decrease in battery performance due to the reaction gas flowing into the gap can be suppressed. Further, the battery can be easily assembled, and the battery component can be made compact by reducing the fastening force of the battery stack, and the separator plate can be made thin by making the space necessary for sealing compact. As a result, the reliability of the battery and the yield during mass production can be improved.

  As described above, the polymer electrolyte fuel cell of the present invention includes a water absorbing material made of a substance that swells due to water absorption in a gap formed between the electrode and the seal member. Thereby, at the time of assembly, a sufficient clearance can be ensured between the seal member and the electrode, so that assembly is facilitated. When the assembled fuel cell is in operation, the water-absorbing material provided in the clearance portion absorbs water in the supplied reaction gas and / or water generated by an electrochemical reaction in the electrode portion and swells. Thereby, a clearance can be made smaller than the time of an assembly. Therefore, the reaction gas can be prevented from flowing out to the clearance, and stable power generation performance can be obtained.

It is preferable that the water absorbing material used here has a form that can be easily installed in the clearance portion during battery assembly. For example, it is preferable to cut out a sheet of the same material as that of the polymer electrolyte membrane in a linear shape, and to install it in the clearance portion so as to be along a part or almost the entire circumference of the electrode.
As the absorbent material, a fibrous or quasi-fibrous polymer material can be installed in the clearance portion along a part or almost the entire circumference of the electrode instead of the material cut out from the sheet.

The water-absorbing material includes perfluorocarbon sulfonic acid, polyacrylate, poly (isobutylene-maleic anhydride), poly (2-acrylamido-2-methylpropanesulfonate), N-vinylacetamide Polymer, polyacrylamide, polyvinyl alcohol, poly (methacryloyloxyethyl quaternized ammonium chloride), N, N-dimethyl-N- (3-acrylamidopropyl) -N- (carboxymethyl) ammonium inner salt polymer, cellulose fiber These may be used, and these may be used alone or as a composite of two or more. For example, it is possible to use a polyacrylate water-absorbent resin for sanitary materials sold under the name of Aqua Keep from Sumitomo Seika Co., Ltd. or a thermoplastic water-absorbent resin sold under the name of Aqua Coke. it can.
The water absorbing material is also preferably acid resistant to withstand long-term use.
Embodiments of the present invention will be described below with reference to the drawings.

A front view of the anode side separator plate is shown in FIG. 1, and a rear view thereof is shown in FIG.
The anode separator plate 10 has a pair of fuel gas manifold holes 12, an oxidant gas manifold hole 13, a cooling water manifold hole 14, a spare manifold hole 15, and four fastening bolt holes 11. .
A surface of the anode separator plate 10 facing the anode is provided with a gas flow path 16 connected to the pair of fuel gas manifold holes 12 to supply fuel gas to the anode. The gas flow path 16 is constituted by four parallel grooves.

  The separator plate 10 has a cooling water flow path 18 communicating with a pair of cooling water manifold holes 14 on the back surface thereof. The flow path 18 is composed of six parallel grooves. On the back surface of the separator plate 10, there are further provided O-ring grooves 12a and 13a for installing an O-ring so as to surround each pair of the fuel gas manifold hole 12 and the oxidant gas manifold hole 13, respectively. ing. Further, on the back surface of the separator plate 10, an O-ring groove 14 a surrounding the cooling water manifold hole 14, the spare manifold hole 15, and the cooling water flow path 14 b is provided.

A front view of the cathode separator plate is shown in FIG. 3, and a rear view thereof is shown in FIG.
The cathode separator plate 20 has a pair of fuel gas manifold holes 22, an oxidant gas manifold hole 23, a cooling water manifold hole 24, a spare manifold hole 25, and four fastening bolt holes 21. .
On the surface of the cathode separator plate 20 facing the cathode, there is provided a gas flow path 27 that communicates with the pair of oxidant gas manifold holes 23 and supplies the oxidant gas to the cathode. The gas flow path 27 includes seven parallel grooves.
The separator plate 20 has a cooling water flow path 28 communicating with the pair of cooling water manifold holes 24 on the back surface thereof. The flow path 28 is composed of six parallel grooves.

FIG. 5 shows a front view of the anode side seal member, and FIG. 6 shows a front view of the cathode side seal member.
The anode-side seal member 30 adhered on the anode-side separator plate 10 is a first closed loop that surrounds the gas flow path 16 and the pair of fuel gas manifold holes 12 in the anode-side separator plate to form one closed loop. An anode side seal portion 37 is provided. The first anode-side seal portion 37 corresponds to the hatched portion in FIG. The anode-side seal member 30 further includes manifold hole seal portions 33, 34, and 35 that independently surround the oxidant gas manifold hole 13, the cooling water manifold hole 14, and the spare manifold hole 15, respectively, and the cathode side. The separator plate 20 has seal portions 38a and 38b surrounding both sides of the portion of the gas passage 27 of the separator plate 20 connected to the manifold hole 23. The manifold hole seal portion 33 is connected to the first anode side seal portion 37 by a connecting portion 39a. The manifold hole seal portions 34 and 35 are connected to each other, and one end portion is connected to the first anode-side seal portion 37 by the connecting portion 39b and the other end portion is connected by the connecting portion 39c.

  On the other hand, the cathode side sealing member 40 bonded to the cathode side separator plate 20 includes a fuel gas manifold hole 42, an oxidant manifold hole 43, a cooling water manifold hole 44 corresponding to each manifold hole in the separator plate 20, And a spare manifold hole 45 and a bolt hole 41, and a notch 47 in a portion corresponding to the cathode.

The anode-side seal member 30 is fixed to the anode-side separator plate 10 by adhering the adhesive layer on the back surface thereof to the surface of the anode-side separator plate 10 facing the anode.
On the other hand, the cathode side sealing member 40 is fixed to the cathode side separator plate 20 by adhering the adhesive layer on the back side to the surface of the cathode side separator plate 20 facing the cathode. .

A unit cell is formed by sandwiching an MEA composed of a pair of electrodes and a polymer electrolyte membrane between the anode side separator plate 10 provided with the anode side seal member 30 and the cathode side separator plate 20 provided with the cathode side seal member 40. Composed.
Generally, a unit cell is assembled using a predetermined assembly jig with a guide pin raised. An example of the assembly procedure is shown below.

  First, the cathode side separator plate 20 provided with the cathode side sealing member 40 is disposed on an assembly jig. The cathode separator plate 20 provided with the cathode side sealing member 40 is shown in FIG. Next, a water absorbing material is disposed along the inner surface of the peripheral edge of the cutout 47 of the cathode side sealing member 40 as shown by a one-dot chain line in FIG. Thereafter, the MEA is disposed on the cathode separator plate 20 along the guide pins. Next, a similar water absorbing material is arranged along the peripheral edge of the anode side gas diffusion layer of the MEA. Furthermore, the anode side separator plate 10 provided with the anode side sealing member 30 is arranged on the MEA.

  When assembling the unit cell according to the above procedure, when assembling the anode separator plate 10, the positional relationship between the MEA and the anode side seal member 30 cannot be visually observed. Sometimes. However, in the anode side sealing member 30 of the present embodiment, a sufficient clearance can be provided between the inner peripheral portion of the cutout portion 47 and the MEA in the anode side sealing member 30 when the unit cell is assembled. . For this reason, the anode side sealing member 30 does not mount on MEA, and the stable sealing performance can be ensured.

  As described above, when the water absorbing material is disposed in the clearance portion between the electrode and the seal member, the water absorbing material can supply water in the reaction gas supplied or water generated by an electrochemical reaction in the electrode portion during battery operation. Absorbs and swells. As a result, the clearance between the electrode and the seal member can be made smaller than that during assembly. Therefore, the outflow of the reaction gas to the clearance part can be suppressed, and stable power generation performance can be obtained.

  Here, the water-absorbing material 51 is arranged almost all around the clearance portion between the electrode and the seal member. However, for example, a water absorbing material may be disposed only in a portion extending to the inlet side manifold hole of the gas flow path, that is, in the vicinity of the gas introduction portion, for example, in a portion indicated by A1 and B1 in FIG. In FIG. 7, a portion extending to the outlet side manifold hole of the gas flow path, that is, the vicinity of the gas discharge portion is represented by A2 and B2. It is preferable to arrange the water absorbing material not only in the portions A1 and B1, but also in the portions A2 and B2. In the case of the structure as shown in FIG. 7, the water absorbing material is not disposed on the portion where the gas flow path 27 is connected to the manifold hole 23. When the cover plate is provided on the portion where the gull flow path is connected to the manifold hole 23, the water absorbing material may be disposed thereon. In the above configuration, the water absorbing material 51 is incorporated as a member independent of the seal member 30. However, the water absorbing material 51 may be integrated with the seal member 30 or the MEA.

Hereinafter, embodiments of the present invention will be described in detail.
Example 1
(I) Production of separator plate By machining an isotropic graphite plate, anode-side separator plate 10 shown in FIGS. 1 and 2 of Embodiment 1 and cathode-side separator plate 20 shown in FIGS. 3 and 4 Was made. The thickness of the separator plate was 3 mm, the grooves of the gas channel and the cooling water channel were 3 mm pitch, and the groove width was 1.5 mm.

(Ii) Production of Seal Member Seal members 30 and 40 having the same pressure-sensitive adhesive layer as in Embodiment 1 shown in FIGS. 5 and 6 were produced as follows.
First, a polyimide film having a thickness of 100 μm was placed on a mold, the mold was fastened, and fluororubber was injection molded under conditions of a temperature of 200 ° C. and an injection pressure of 150 kg / cm ² . Next, secondary crosslinking was carried out at 200 ° C. for 10 hours to form a fluororubber layer having a thickness of 125 μm. Thereafter, an adhesive layer made of butyl rubber and having a thickness of 25 μm was joined to the back surface of the polyimide film by transfer, and the surface of the adhesive layer was covered with a release film made of polypropylene. Then, the sealing member of the predetermined shape was produced by punching with a punching die.
The sealing members 30 and 40 obtained as described above were set on the separator plates 10 and 20, respectively, and bonded by hot pressing at 100 ° C. with a pressing load of 2000 kgf for 1 minute.

(Iii) Preparation of MEA Platinum particles having an average particle size of about 30 mm were supported on an acetylene black carbon powder in a weight ratio of 4: 1 to obtain a catalyst powder for an electrode. This catalyst powder was dispersed in isopropanol. This was mixed with an ethyl alcohol dispersion of perfluorocarbon sulfonic acid powder to obtain an electrode paste. By applying this electrode paste as a raw material by screen printing, it was applied to one surface of a 250 μm thick carbon nonwoven fabric to form a catalyst layer to obtain an electrode. Amount of platinum contained in the catalyst layer is 0.5 mg / cm ^2, the amount of perfluorocarbon sulfonic acid was 1.2 mg / cm ^2.

These electrodes have the same configuration for both the positive electrode and the negative electrode, and the apparent area is 100 cm ² . An electrolyte membrane / electrode assembly (MEA) was produced by sandwiching a hydrogen ion conductive polymer electrolyte membrane with the catalyst layer inside with a pair of electrodes produced in this manner and hot pressing. A perfluorocarbon sulfonic acid membrane having a thickness of 25 μm was used as the hydrogen ion conductive polymer electrolyte membrane.
The size of the polymer electrolyte membrane is the same as the size of the separator plate described later, and the polymer electrolyte membrane corresponds to a pair of fuel gas manifold holes, cooling water manifold holes, and oxidant gas manifold holes in the separator plate. A hole was formed by a punching die.

(Iv) Production of water-absorbing material A film of perfluorocarbon sulfonic acid having an area of 1600 cm ² and a thickness of 125 μm (not heat-treated like that used for polymer electrolyte membranes) cut to a width of 150 μm Using. This water absorbing material 51 is shown in FIG. About this water absorbing material, the elution test was done in the following procedures.
1 g of the water absorbing material was put into 50 cc of water and left at 90 ° C. for 50 hours. Thereafter, various substances eluted in water were analyzed. As a result, NH ₃ <1 ppm, TOC <100 ppm, and halogen <1 ppm.

(V) Assembly of laminated battery Unit obtained by sandwiching MEA having an electrode area of 100 cm ² by the anode-side separator plate 10 provided with the anode-side seal member 30 and the cathode-side separator plate 20 provided with the cathode-side seal member 40 obtained above. A battery was constructed. At this time, O-rings were installed in the O-ring grooves 12a to 14a of the anode separator plate 10, respectively. When the unit cells are stacked, the surface of the separator plate 10 having the cooling water channel 18 and the surface of the adjacent unit cell separator plate 20 having the cooling water channel 28 are stacked so as to face each other. Thus, a cooling unit was provided.

The procedure for assembling the cell will be described below.
A predetermined assembly jig with a guide pin placed thereon was placed, and the cathode side separator plate 20 provided with the cathode side seal member 40 was placed thereon. Next, the water absorbing material 51 was disposed along the inner surface of the peripheral edge portion of the cutout portion 47 of the cathode side sealing member 40 as shown by a one-dot chain line in FIG. Thereafter, the MEA was disposed along the guide pins. At that time, the MEA was carefully assembled to the cathode side separator plate so that the cathode of the MEA would not be placed on the water absorbing material 51 arranged at the peripheral edge of the notch 47 in the cathode side sealing member 40. A clearance is required between the guide pins installed on the assembly jig and these members to be assembled.

  Since the size of the MEA greatly changes depending on the humidity during assembly, it is necessary to provide a large clearance between the MEA and the guide pin. In order to assemble the MEA stably, the clearance between the guide pin and the MEA required 1 mm. After installing the MEA, the water absorbing material 51 was disposed along the peripheral edge of the anode side gas diffusion layer of the MEA. However, no water-absorbing material is disposed on the portion of the anode separator plate to be assembled thereafter in contact with the gas flow path. Thereafter, the anode separator plate 10 provided with the anode side sealing member 30 was assembled. At this time, a clearance of 1.0 mm between the anode and the electrode seal portion 37 in the anode side sealing member 30 was secured. Since the separator plate 10 is opaque and the assembled state of the anode side separator plate 10 to the MEA cannot be visually observed, the anode side separator plate 10 was assembled according to the guide pins.

By repeating the above assembly process, 50 cells are stacked, stainless steel end plates are arranged on both ends of the stack through current collector plates and insulating plates, and fastened with a fastening load of 1000 kgf by a fastening rod did. This laminated battery is referred to as battery A. When the laminated battery thus produced was operated, the water absorbing material disposed in the clearance portion absorbed water and swelled, so that there was almost no clearance. At this time, as a result of confirming the pressure applied to the MEA and the separator plate with the pressure sensitive paper, the pressure applied to the MEA was 10 kgf / cm ² .

The battery A was checked for gas leaks. The outlet side manifold hole was closed, and He gas was introduced from the inlet side manifold hole at a pressure of 0.5 kgf / cm ² , and the inflow gas flow rate at that time was examined. There was no gas leak on the oxidant gas side, the fuel gas side, and the cooling water side, and it was confirmed that the battery A had no problem in fluid sealability.

<< Comparative Example 1 >>
A battery B was produced in the same procedure using the assembly jig as in Example 1 except that the water absorbing material was not disposed on the anode side and the cathode side. At this time, the clearance between the gasket and the electrode was 0.25 mm on the anode side and the cathode side, respectively.

The battery B was checked for gas leakage under the same conditions as in Example 1. Since the fastening load was 1000 kgf and the pressure applied to the MEA was 10 kgf / cm ² , the fastening pressure was 1000 kgf. As a result, in some of the single cells, a leak to the outside of the gas or a cross leak from the oxidant gas side to the fuel gas side or both occurred, resulting in poor sealing.

<< Comparative Example 2 >>
A battery C was produced in the same manner as in Comparative Example 1 except that the clearance between the gasket and the electrode was 1.0 mm on the anode side and the cathode side, respectively. The assembly of the members was performed in the same procedure using the assembly jig as in Example 1.

The battery C was subjected to a gas leak check under the same conditions as in Example 1. Since the fastening load was 1000 kgf and the pressure applied to the MEA was 10 kgf / cm ² , the fastening pressure was 1000 kgf. As a result, there were no gas leaks on the oxidant side, fuel gas side, and cooling water side, and it was confirmed that there was no problem in fluid sealing performance as a laminated battery.

  After performing a leak check, the batteries A to C of Example 1 and Comparative Examples 1 and 2 were disassembled and the assembly condition was confirmed. In all the batteries, the anode in the MEA was assembled with a slight deviation from the center of the anode side sealing member. In the batteries A and C of Example 1 and Comparative Example 2, the part that seals the periphery of the electrode is on the outside with a sufficient margin than the electrode, so that it is possible to ensure the sealing performance in the electrode displacement range during assembly. I found out that On the other hand, in the battery B of Comparative Example 1, the electrodes were similarly shifted. And it turned out that a part of electrode goes up on a sealing member, a sealing performance is impaired, and a sealing defect arises.

The unit cell is assembled by installing the MEA on the cathode separator and then assembling the anode separator plate. At this time, it is desirable that the anode of the MEA be installed at the center of the anode side sealing member. However, misalignment occurs due to accumulation of assembly jig clearance, MEA dimensional error, and separator plate dimensional error.
Stable assembly is possible if the degree of assembly between the anode and the anode-side seal member can be visually confirmed, but the separator plate is opaque and cannot be visually observed, and is assembled according to the guide pins.

  In the case of a conventional flat seal member, the electrode is placed on the seal member in the vicinity of the upper limit of the assumed positional deviation, and the sealing performance cannot be ensured. If the clearance is increased in order to improve the assemblability, the reaction gas flows out to the clearance and is not supplied to the electrode, so that the power generation performance is lowered.

  On the other hand, in the fuel cell of the present invention, since there is sufficient clearance between the seal member and the electrode, even if the electrode is displaced due to dimensional deviation, it is not placed on the seal member, and sealing performance can be ensured. Further, when the manufactured battery is operated, the water absorbing material absorbs moisture and swells, so that the clearance between the electrode and the sealing member decreases. Therefore, the same effect as when the clearance is set small from the beginning can be obtained.

  The battery A of Example 1 and the battery C of Comparative Example 2 were kept at 75 ° C., and the humidified and heated hydrogen gas was adjusted to a dew point of 70 ° C. on the anode side, and the dew point of 60 ° C. was set on the cathode side. Humidified and warmed air was supplied. As a result, an open voltage of 50 V was obtained at the time of no load when neither battery supplies power to the outside. It was also confirmed that there were no problems such as gas cross leaks and short circuits.

Furthermore, the fuel utilization rate is 80%, the current density is 0.3A / cm ² , the dew point of hydrogen gas is 70 ° C, the dew point of air is 65 ° C, and the oxidant utilization rate is changed from 20% in increments of 5% every 12 hours. The power generation was started under the conditions. Then, the stability of power generation under these conditions was investigated. The evaluation results are shown in FIG. In the battery C of Comparative Example 2, the output voltage became unstable when the oxidant utilization rate was 40% or more, and the output voltage decreased when the oxidant utilization rate was 50%. On the other hand, in the battery A of Example 1, a stable output voltage was obtained until the oxidant utilization rate exceeded 65%.

  From this, in the battery C of Comparative Example 2, the clearance between the electrode and the flat seal member allows the reaction gas to easily flow into the clearance, and the amount of the reaction gas necessary to maintain the battery performance. It was found that could not be supplied to the electrode. On the other hand, in the battery of Example 1, the clearance between the electrode and the seal member is large when the laminated battery is assembled, but the clearance between the electrode and the seal member is reduced during operation of the completed battery. It was found that the inflow of the reaction gas into the clearance can be reduced and the deterioration of the battery performance can be prevented.

Example 2
A fibrous water-absorbing material having a diameter of 150 μm and a length of 400 mm based on an isobutylene-maleic anhydride copolymer was used. This water absorbing material 52 is shown in FIG. With respect to this water-absorbing material, various substances eluted in water under the same conditions as in Example 1 were analyzed. As a result, NH ₃ <1 ppm, TOC <100 ppm, and halogen <1 ppm.
A laminated battery D was produced using the same members as in Example 1 except that the above water-absorbing material was used.
The battery had no problem in fluid sealability due to a leak check immediately after assembly, and exhibited similar battery performance under the same conditions as in Example 1.

As described above, according to the present invention, it is possible to ensure sealing performance with highly reliable assembly, reduce the outflow of reaction gas to the clearance by reducing the clearance, and improve the battery performance associated therewith. Further, it becomes possible to abolish post-processing of the separator plate by reducing the accuracy of the guide portion necessary for the separator plate at the time of assembly, to improve the manufacturing yield, and to reduce the cost associated therewith.
Furthermore, since the fastening force required for fastening the laminated battery can be greatly reduced, the fastening member of the laminated body can be simplified and made into a resin. That is, it is possible to reduce the size and cost of the laminated battery.

  As described above, according to the present invention, it has a highly reliable assembly property, and has a stable output characteristic by reducing the clearance between the seal member and the electrode during operation of the completed laminated battery. A polymer electrolyte fuel cell can be provided. Therefore, the polymer electrolyte fuel cell according to the present invention can be applied to uses such as a portable power source, a power source for portable devices, a power source for electric vehicles, and a domestic cogeneration system.

It is a front view of the anode side separator board in one Example of this invention. It is a rear view of the anode side separator plate. It is a front view of the cathode side separator board in one Example of this invention. It is a rear view of the cathode side separator plate. It is a front view of the anode side sealing member in one Example of this invention. It is a front view of the cathode side sealing member in one Example of this invention. It is a front view of the cathode side separator which combined the cathode side sealing member. It is a perspective view of the water absorption material in one Example of this invention. It is a perspective view of the water absorption material in the other Example of this invention. It is a figure which shows the output characteristic of the battery A of Example 1 and the battery C of the comparative example 2 of this invention.

Explanation of symbols

10 Anode separator plate 11, 21, 41 Fastening bolt hole 12, 22, 42 Fuel gas manifold hole 13, 23, 43 Oxidant gas manifold hole 14, 24 Cooling water manifold hole 16, 27 Gas flow path 18 , 28 Flow path for cooling water 20 Cathode side separator plate 30 Anode side seal member 51, 52 Water absorbing material

Claims (3)

  Hydrogen ion conductive polymer electrolyte membrane, a pair of electrodes disposed on both sides of the polymer electrolyte membrane, a pair of conductive separator plates having a gas flow path for supplying a reaction gas to the electrodes, and the electrode and the conductive separator A pair of sealing members that maintain airtightness between the plate and a water absorbing material made of a substance that swells due to water absorption, at least part of a gap portion formed between the electrode and the sealing member. A polymer electrolyte fuel cell.   The polymer electrolyte fuel cell according to claim 1, wherein the water absorbing material is made of a polymer material.   The polymer electrolyte fuel cell according to claim 1 or 2, wherein the water absorbing material has acid resistance.

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