JP2006269264A - Solid polymer electrolyte fuel cell - Google Patents

Abstract

[Objective] To obtain a gas which can be operated at a high gas utilization rate and can be easily assembled by flowing through a gas flow groove of a single cell without leakage of reaction gas.
[Structure] In a structure in which a membrane electrode assembly is sandwiched between separators to form a single cell, a fuel gas circulation groove 7 and a fuel gas are arranged on the separator 10 on the fuel electrode side so as to face the diffusion layer of the membrane electrode assembly. Convex grooves 8a are provided on the side of the diffusion layer side of the packing groove 8 that surrounds the inlet manifold 1 and the fuel gas outlet manifold 2, and the packing is press-fitted by compression so that the gap between the diffusion layer and the packing groove 8 is provided. The gap is closed and the gas flow is blocked.
[Selection] Figure 1

Description

  The present invention relates to a solid polymer electrolyte fuel cell using a polymer membrane as an electrolyte, and in particular, leakage of a reaction gas outside a predetermined flow path is effectively avoided, stable power generation operation can be performed, and assembly. It is related with the battery structure which is easy.

  A polymer electrolyte fuel cell (PEFC) is a fuel cell using a polymer membrane as an electrolyte, and has excellent features such as high output density and long battery life. FIG. 5 is a schematic cross-sectional view showing a conventional general configuration example of a single cell of a solid polymer electrolyte fuel cell. As seen in this figure, the single cell includes a membrane electrode assembly (hereinafter referred to as MEA), a separator 10 on the fuel electrode side provided with the fuel gas flow groove 7 and an oxidant gas flow groove 15. The MEA is sandwiched between the oxidant-side separator 11 and the packing 13 is interposed. The MEA is formed on both sides of the solid polymer film 21 supported by the frame-shaped protective sheet 24 and on the diffusion layer 23. The electrode is formed by joining the electrode formed by forming the catalyst layer 22. A perfluorosulfonic acid polymer is usually used for the solid polymer film 21, and a general-purpose plastic film such as PET (polyethylene terephthalate) is often used for the protective sheet 24. The diffusion layer 23 constituting the electrode functions to diffuse the reaction gas supplied to the gas flow path of the separator to the catalyst layer 22 and to collect the current obtained by the battery reaction. Also plays.

  The separator functions to separate the fuel gas and the oxidant gas from each other, to pass the reaction gas and cooling water, and to conduct the current obtained by the cell reaction to the outside. FIG. 6 is a plan view seen from the MEA side of the separator 10 on the fuel electrode side used in the single cell shown in FIG. As can be seen in the figure, the separator 10 has six manifolds consisting of through holes, namely, a fuel gas inlet manifold 1, a fuel gas outlet manifold 2, an oxidant gas inlet manifold 3, an oxidant gas outlet manifold 4, and a cooling member. A water inlet manifold 5 and a cooling water outlet manifold 6 are provided, and further, a fuel gas circulation groove 7 including a meandering flow path connecting the fuel gas inlet manifold 1 and the fuel gas outlet manifold 2 is provided. Further, a packing groove 8 is provided so as to surround the fuel gas system including the fuel gas inlet manifold 1, the fuel gas outlet manifold 2, and the fuel gas circulation groove 7, and packing is attached to the packing groove 8. The fuel gas system is separated by tightening between the protective sheets. The oxidant gas inlet manifold 3, the oxidant gas outlet manifold 4, the cooling water inlet manifold 5, and the cooling water outlet manifold 6 are each provided with a packing in a packing groove 9 provided around the oxidant gas inlet manifold 3, the cooling water inlet manifold 5, and the protective sheet. Separated by clamping in between.

Generally, a carbon composite material composed of carbon powder and resin is used as the constituent material of the separator 10. As the carbon powder, flake graphite powder, artificial graphite, expanded graphite, carbon black, or the like is used. Further, the resin may be either a thermosetting resin or a thermoplastic resin, and generally a phenol resin or an epoxy resin is used. The separator is produced by molding a compound obtained by mixing these carbon powder and resin, or by injection molding. Further, as a packing material to be mounted in the packing groove 8 and the packing groove 9, fluorine rubber, ethylene propylene rubber, silicon rubber, or the like is used.
A solid polymer electrolyte fuel cell is composed of a fuel cell stack in which a plurality of single cells as described above are stacked. FIG. 7 is a side view schematically showing the solid polymer electrolyte fuel cell configured as described above. A number of unit cells 31 corresponding to the required generated voltage are stacked, current collector plates 32 for taking out DC power at both ends, an insulating plate 33 for electrically insulating the stack from the structural member, and a clamping plate 34 Furthermore, a solid polymer electrolyte fuel cell is configured by arranging a coil spring 35 between the end plate 36 supported by the stud 37 and the clamping plate 34, and the stack of the single cells 31 is a coil. The spring 35 is pressurized and supported at a constant tightening pressure. By supporting the pressure in this way, the contact resistance between the laminated parts such as between the MEA of the single cell 31 and the separator or between the adjacent single cells 31 and 31 is reduced, and the electrical loss is suppressed. Is done. Moreover, the packing interposed between the protective sheet of the single cell 31 and the separator is crushed by the pressure support of the stack, and the adhesion between the protective sheet and the packing and between the separator and the packing is improved. Thus, the gas sealing performance is improved.

  As described above, in the solid polymer electrolyte fuel cell, the stack is pressurized and supported to improve electrical characteristics and gas sealing performance. However, when a fuel cell is actually manufactured, a deviation may occur with respect to a design value due to processing tolerances, assembly tolerances, and the like. For example, in the single cell used in the above-described conventional fuel cell, the packing used for gas sealing is configured to be interposed between the protective sheet and the packing groove of the separator. In such a battery, there is a possibility that the positional deviation occurs due to processing tolerance, assembly tolerance, etc., and the packing may come off the protective sheet and overlap the diffusion layer of the MEA. If the packing overlaps the diffusion layer in this way, there is a risk that the diffusion layer may be destroyed or the gas tightness may be impaired. Therefore, it is essential to avoid the packing from overlapping the diffusion layer. For this reason, it is necessary to make the inner dimension of the packing groove disposed surrounding the diffusion layer sufficiently larger than the outer dimension of the diffusion layer.

However, if a sufficient distance is taken between the inner dimension of the packing groove and the outer dimension of the diffusion layer in this way, the reaction gas can flow into the gap, and thus supplied from the manifold. A part of the reaction gas flows through this gap and flows through the gas flow path arranged facing the diffusion layer. The flow rate of the reaction gas that contributes to the battery reaction is lower than the predetermined flow rate, and the battery characteristics deteriorate. There is a fear. Therefore, in order to stably obtain a predetermined battery characteristic, it is necessary to block the flow of the reaction gas to the gap. For example, as disclosed in Patent Document 1, a filling seal is appropriately provided in the gap. A method of filling and blocking the flow of gas is used.
JP 2004-119121 A

As described above, in this type of solid polymer electrolyte fuel cell, in order to avoid the destruction of the diffusion layer of the single cell and the loss of gas tightness that may occur due to pressurization and support of the stack, In order to suppress a decrease in power generation characteristics due to the gas flowing by bypassing the gap between the inner dimension of the packing groove and the outer dimension of the diffusion layer, and further bypassing the gap therebetween, Measures such as filling the gap with a filling seal and blocking the flow path are taken.
If the method of sealing with a filling seal is used in this way, degradation of power generation characteristics can be avoided, but since a separate filling seal is required, the number of manufactured parts increases and the manufacturing process increases, which increases the manufacturing cost. Become. In addition, although the method of making said filling seal into a component integrated with packing is also conceivable, in this method, interference occurs between the filling seal and the diffusion layer at the time of assembly, and the problem is that assembly cannot be performed easily. There is a point.

  The present invention has been made in consideration of the problems of the conventional solid polymer electrolyte fuel cells as described above, and an object of the present invention is to provide a single-cell MEA and separator that are stacked, pressurized, and supported. Gas seal packing inserted between the two is properly installed without increasing the number of parts used, and the gas in the single cell is effectively sealed, and stable power generation operation is continued. It is an object of the present invention to provide a solid polymer electrolyte fuel cell that can be manufactured at low cost.

In order to achieve the above object, in the present invention,
A membrane electrode assembly formed by arranging an electrode composed of a catalyst layer and a diffusion layer on both sides of a solid polymer electrolyte membrane, a gas flow groove provided in a region facing the electrode, and a gas flow groove In a solid polymer electrolyte fuel cell comprising a single cell sandwiched between a pair of separators each having a gas inlet manifold and a gas outlet manifold each having a communicating through hole.
(1) A packing groove that surrounds the gas flow groove, the gas inlet manifold, and the gas outlet manifold and is provided with a packing for gas sealing is provided, and extends to the side surface of the electrode along the electrode side of the packing groove. When the battery has a convex groove and is assembled by pressurizing and tightening the battery, the packing attached to the packing groove is press-fitted into the convex groove and extended to the side surface of the electrode. It shall be configured.

(2) Also, in the solid polymer electrolyte fuel cell of (1) above, the electrode side of the packing groove connected to the vicinity of the gas inlet manifold and the vicinity of the gas outlet manifold and disposed on both sides with the gas flow groove interposed therebetween Each of the convex grooves is provided with at least one convex groove.
(3) Further, in the solid polymer electrolyte fuel cell according to (1) or (2), the convex groove is provided on the creeping surface of the bent portion of the packing groove on the electrode side.

  In a solid polymer electrolyte fuel cell comprising a single cell constructed by sandwiching an MEA with a pair of separators having gas flow grooves, as described in (1) above, the gas flow grooves and the gas flowing through the gas flow grooves are A packing groove is provided so as to surround the gas inlet manifold and the gas outlet manifold, and a convex groove extending to the side surface of the electrode is provided along the electrode side of the packing groove, and the battery is assembled by press-tightening the battery. When the packing mounted in the packing groove is press-fitted into the convex groove and extended to the side surface of the electrode, the packing is pressed into the convex groove and the side surface of the electrode. The gap between the packing groove and the side surface of the electrode is partially filled by the packing member that extends to the side. Therefore, the gas flow through the gap is prevented, and the gas flows from the gas inlet manifold to the gas outlet manifold via the gas flow groove without leaking. Further, in this configuration, since the gap is filled with the packing member press-fitted into the convex groove, the gas flow can be easily prevented even if the gap is not minute. Therefore, since the size of the gap between the packing groove and the side surface of the electrode can be widened, the single cell can be easily assembled and stacked.

Further, as described in the above (1), in the case where a gas flow groove, a gas inlet manifold and a gas outlet manifold are surrounded and a packing groove is provided, and packing is attached to the packing groove to seal the gas, May flow from the gas inlet manifold to the gas outlet manifold through a gap formed between the opposing electrode of the gas flow groove and the packing. Therefore, as described in (2) above, if each of the convex grooves on the electrode side of the packing groove disposed on both sides of the gas flow groove is provided with at least one convex groove, the gas flow groove is The flow of gas that does not circulate is completely cut off, and the fuel cell of this configuration can be stably operated with a predetermined battery performance.
Further, in the unit cell configured as described above, the compressive force concentrates on the bent portion of the packing when the unit cell is assembled or when the stack is pressed and tightened. If the groove is provided on the creeping surface of the packing groove on the electrode side, a compressive force is effectively applied to the packing of the convex groove portion, and the packing member press-fitted into the convex groove effectively removes the gap. To ensure stable power generation.

The best embodiment of the solid polymer electrolyte fuel cell of the present invention is:
MEA formed by arranging an electrode composed of a catalyst layer and a diffusion layer on both sides of a solid polymer electrolyte membrane having a peripheral edge sandwiched between protective sheets, a gas flow groove in the region facing the electrode, and In the solid polymer electrolyte fuel cell comprising a single cell configured to be sandwiched between a pair of separators each having a gas inlet manifold and a gas outlet manifold each having a through hole in a region facing the peripheral edge portion, The gas flow groove and a gas groove that surrounds the gas flow groove and the gas outlet manifold are provided in a region facing the peripheral edge, and a packing groove for mounting a gas seal packing is provided. When the packing groove is provided with a convex groove extending to the side surface of the electrode on the side of the electrode, and the battery is assembled by press-tightening, The packing is mounted in grayed groove is pressed into convex grooves described above, in the configuration form to be arranged extending into the side surface of the electrode.

A single cell of the solid polymer electrolyte fuel cell of the present invention was produced by the following method.
First, a platinum-ruthenium alloy-supported carbon catalyst in which a platinum-ruthenium alloy (alloy ratio 2: 1) is supported on a carbon support and an electrolyte resin solution (manufactured by DuPont, Nafion solution) are mixed to form a catalyst dispersion slurry for an anode. Was made. Next, in a 105 mm × 105 mm region on the gas diffusion layer consisting of a carbon paper base material (Toray, TGPH60, 120 mm × 120 mm, thickness 190 μm) treated with PTFE (polytetrafluoroethylene). The slurry was applied to make an anode electrode. In addition, it apply | coated so that the catalyst amount might be set to 0.7 mgPt / cm < ² > at this time.
Next, a platinum-supported carbon catalyst in which platinum is supported on a carbon carrier and an electrolyte resin solution (manufactured by DuPont, Nafion solution) are mixed to prepare a catalyst dispersion slurry for the cathode, and this slurry is made water-repellent by PTFE. A cathode electrode was prepared by applying a 105 mm × 105 mm region on a gas diffusion layer made of a treated carbon paper substrate (Toray, TGPH60, 120 mm × 120 mm, thickness 190 μm). In addition, it apply | coated so that the catalyst amount might be set to 0.7 mgPt / cm < ² > at this time.

  Further, Nafion N-112 (160 mm × 160 mm, thickness 50 μm) manufactured by DuPont was prepared as an electrolyte membrane, and this was sandwiched between frame-shaped protective sheets. The protective sheet consists of a 25 μm thick PEA (polytetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) sheet, and the outer shape is 160 mm × 160 mm, the same as the electrolyte membrane, with a 100 mm × 100 mm square hole in the center. Is provided. Therefore, when the electrolyte membrane is sandwiched between the protective sheets, the electrolyte membrane is exposed from the hole portion. This chargeable film was sandwiched between the anode electrode and the cathode electrode prepared as described above, and hot pressing was performed to prepare an MEA. At this time, the anode electrode and the cathode electrode are arranged and sandwiched so that each catalyst layer faces the chargeable membrane, set in a hot press apparatus, and hot under the conditions of a temperature of 140 ° C., a pressure of 5 MPa, and a time of 5 min. Pressed.

On the other hand, as a separator used in combination with this MEA, a separator in which a gas channel was formed by molding a compound obtained by mixing carbon powder and resin was used. At this time, flake graphite powder was used as the carbon powder, and phenol resin was used as the resin. In addition, a gas flow groove disposed opposite to the electrode of the MEA and a packing groove that surrounds a gas flow path composed of a gas inlet manifold and a gas outlet manifold for the gas flowing in the gas flow groove are formed. Convex grooves extending toward the side surfaces of the electrodes were provided on the creeping surfaces on the electrode side in the vicinity of the gas inlet manifold and the gas outlet manifold, that is, on the creeping surface on the gas flow groove side. The packing groove was a rectangular cross-sectional groove having a width of 3 mm and a depth of 1 mm, and the convex groove was a semicircular groove having a radius of 0.5 mm.
FIG. 1 is a schematic front view of a separator on the fuel electrode side of a single cell of this example. Also in this figure, components having the same functions as those of the conventional example shown in FIG. 6 are denoted by the same reference numerals, 10 is a separator on the fuel electrode side, Reference numerals 5 and 6 denote a fuel gas inlet manifold, a fuel gas outlet manifold, an oxidant gas inlet manifold, an oxidant gas outlet manifold, a cooling water inlet manifold, and a cooling water outlet manifold each having a through hole. Reference numeral 7 denotes a fuel gas circulation groove comprising a meandering flow path connecting the fuel gas inlet manifold 1 and the fuel gas outlet manifold 2, and 8 denotes a packing groove surrounding these fuel gas systems. The difference between the separator of this embodiment and the separator of the conventional example shown in FIG. 6 lies in the seal structure of the fuel gas system. The feature of this embodiment is that the packing groove 8 surrounding the fuel gas system is incorporated in the diffusion layer. Convex grooves 8a and 8b are provided along the fuel gas flow groove 7 side facing the region.

  Various materials such as fluorine rubber, ethylene propylene rubber, and silicon rubber can be used for the packing to be mounted in the packing groove 8 described above. In this example, the width obtained by molding fluoro rubber was 3 mm, A packing with an oval cross section of 1.5 mm in height was attached. FIG. 2 is a schematic front view of the main part showing the configuration of the fuel electrode side separator 10 in the vicinity of the fuel gas inlet manifold 1, and a mounting situation when a packing having the same width as the groove width is fitted into the packing groove 8. Is shown. In this figure, 13 is a packing mounted in a packing groove surrounding the fuel gas system, 14 is a packing mounted in a packing groove surrounding the cooling water inlet manifold 5, and 20 is an MEA disposed opposite to the separator. The position of the diffusion layer is shown. In this configuration, since the packing 13 has the same width as the packing groove 8, the packing 13 is inserted into the packing groove 8 in an orderly manner, as shown in this figure, after mounting and before tightening, and the convex groove 8a No entry into. Therefore, when the MEA is sandwiched between the separators to form a single cell, it is easy to maintain a sufficient gap between the MEA diffusion layer and the packing 13, and the assembly performance is improved.

  FIG. 3 is a schematic cross-sectional view of a single cell in which the separator and the MEA are aligned so that the outer dimension position of the diffusion layer is 0.5 mm inside the packing groove 8 inner dimension position. This figure constitutes a single cell by sandwiching an MEA composed of a solid polymer membrane 21 supported by a frame-shaped protective sheet 24, a catalyst layer 22 and a diffusion layer 23 between two separators 10 and 11, The difference from the conventional example shown in FIG. 5 resides in a convex groove 8 a provided in the packing groove 8. In the state before the single cell is tightened, as shown in FIG. 2, no packing has entered the convex groove 8a. Thirty single cells aligned in this way were stacked and tightened with a tightening member to form a fuel cell stack. At this time, the tightening pressure was set so that the surface pressure at the surface where the separators 10 and 11 and the MEA contact each other was 0.6 MPa. FIG. 4 is a schematic cross-sectional view of a single cell that is aligned and tightened as shown in FIG. The packing 13 is compressed by the tightening, and the expansion force in the side surface direction of the packing groove 8 works to enter the convex groove 8a. When the packing 13 enters the convex groove 8a in this manner, the gap between the MEA diffusion layer 23 and the packing 13 is filled with the packing that has entered the convex groove 8a. This will prevent the gas from flowing.

A fuel cell stack constructed by stacking and fastening 30 single cells as described above, using a mixed gas of 80% H ₂ + 20% CO ₂ as an anode reaction gas and air as a cathode reaction gas, and a stack temperature of 80 ° C. A power generation experiment was conducted under conditions of an anode humidification temperature of 70 ° C., a cathode humidification temperature of 70 ° C., a current density of 0.4 A / cm ² , and normal pressure. As a result, it was confirmed that the solid polymer electrolyte fuel cell using the single cell according to the configuration of this example can be stably operated at a fuel utilization rate of 85% and an air utilization rate of 60%. This value greatly exceeds the upper limit of stable operation of a solid polymer electrolyte fuel cell using a single cell having a conventional configuration (fuel utilization rate 80%, air utilization rate 55%). It has been found that the flow of the reaction gas flowing through the gap between the diffusion layer and the packing is effectively cut off, and the reaction gas is effectively used to improve the power generation efficiency.

  As described above, the MEA formed by arranging the electrode composed of the catalyst layer and the diffusion layer on both surfaces of the solid polymer electrolyte membrane having the peripheral portion sandwiched between the protective sheets is formed in the region facing the electrode. A solid polymer electrolyte type comprising a single cell comprising a flow groove and sandwiched between a pair of separators each having a gas inlet manifold and a gas outlet manifold each having a through hole in a region facing the peripheral edge portion. In the fuel cell, as in the present invention, the gas flow groove and the gas inlet manifold and the gas outlet manifold of the gas flowing through the gas flow groove are surrounded in the region of the separator facing the peripheral edge portion, and the gas seal is used. A packing groove for mounting the packing, a convex groove extending to the side surface of the electrode on the electrode side of the packing groove, and a battery. When assembled by tightening and assembling, the packing mounted in the packing groove is press-fitted into the above-mentioned convex groove and is arranged to be extended to the side surface of the electrode. The gas is properly and easily installed and the gas in the single cell is effectively sealed without increasing the power consumption. A solid polymer electrolyte fuel cell that can be used can be obtained. Therefore, the present invention can be effectively applied to solid polymer electrolyte fuel cells for various uses.

Schematic front view of a separator on the fuel electrode side incorporated in a single cell of an embodiment of the present invention The principal part front schematic diagram which shows the structure of the fuel gas inlet manifold vicinity of the separator of the fuel electrode side of the Example of this invention. Schematic cross-sectional view showing the structure before tightening the single cell of the embodiment of the present invention Sectional schematic diagram which shows the structure after the fastening of the single cell of the Example of this invention Cross-sectional schematic diagram showing an example of a conventional general configuration of a single cell of a solid polymer electrolyte fuel cell The top view seen from the MEA side of the separator 10 of the fuel electrode side used for the single cell of FIG. 5 is a side view schematically showing a solid polymer electrolyte fuel cell configured using the single cell of FIG.

Explanation of symbols

1 Fuel gas inlet manifold
2 Fuel gas outlet manifold
3 Oxidant gas inlet manifold
4 Oxidant gas outlet manifold
7, 7a Fuel gas distribution groove
8 Packing groove
8a, 8b Convex groove
9 Packing groove 10 Separator 13 Packing 14 Packing 21 Solid polymer membrane 22 Catalyst layer 23 Diffusion layer 24 Protective sheet

Claims (4)

A membrane electrode assembly formed by arranging an electrode composed of a catalyst layer and a diffusion layer on both sides of a solid polymer electrolyte membrane, a gas flow groove provided in a region facing the electrode, and a gas flow groove In a solid polymer electrolyte fuel cell comprising a single cell sandwiched between a pair of separators each having a gas inlet manifold and a gas outlet manifold each having a communicating through hole.
A packing groove surrounding the gas flow groove, the gas inlet manifold and the gas outlet manifold, and having a gas seal packing mounted thereon;
On the creeping side of the packing groove on the electrode side, it has a convex groove extending to the side surface of the electrode,
In addition, when the battery is assembled by pressurizing and tightening, the packing attached to the packing groove is press-fitted into the convex groove and extended to the side surface of the electrode. Electrolytic fuel cell. In the solid polymer electrolyte fuel cell according to claim 1, the gas inlet manifold vicinity and the gas outlet manifold vicinity are connected, and the packing groove disposed on both sides across the gas flow groove has a creeping surface on the electrode side, respectively. A solid polymer electrolyte fuel cell comprising at least one convex groove. 3. The solid polymer electrolyte fuel cell according to claim 1, wherein the convex groove is provided on a surface on the electrode side of a bent portion of the packing groove. 4. battery. 4. The solid polymer electrolyte fuel cell according to claim 1, wherein the packing is a molded rubber packing made of fluorine rubber or ethylene propylene rubber.

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