JP4083304B2 - Polymer electrolyte fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a room temperature operation type solid polymer fuel cell used for a portable power source, a power source for electric vehicles, a domestic cogeneration system, and the like.
[0002]
[Prior art]
A polymer electrolyte fuel cell is one in which a fuel such as hydrogen and an oxidant gas such as air are electrochemically reacted by a gas diffusion electrode to simultaneously supply electricity and heat.
A catalytic reaction layer mainly composed of carbon powder carrying a platinum-based metal catalyst is formed on both surfaces of the polymer electrolyte membrane that selectively transports hydrogen ions. On the outer surface of the catalyst reaction layer, a pair of diffusion layers having both gas permeability and conductivity are formed in close contact with each other, and this and the catalyst reaction layer together constitute an electrode.
Outside the electrodes, a conductive separator plate is disposed to mechanically fix the joined body of these electrodes and electrolyte, and to electrically connect adjacent joined bodies to each other in series. In the portion of the separator plate that comes into contact with the electrode, a gas flow path is formed for supplying the reaction gas to the electrode surface and carrying away the generated gas and surplus gas.
[0003]
The structure of the unit cell of this type of fuel cell will be described with reference to the drawings.
In FIG. 10, the polymer electrolyte membrane 3 is sandwiched between a pair of electrodes 1 having a catalytic reaction layer 2, and the periphery of the electrolyte membrane is sandwiched between a pair of sealing materials 17, and these are sandwiched between a pair of separator plates 4. The unit cell of a structure is shown. The separator plate 4 has a gas flow path 5 for supplying fuel gas and oxidant gas to the electrode 1. The sealing material 17 prevents hydrogen in the fuel and air in the oxidant from leaking out of the battery or mixing with each other. A separator plate having a gas flow path on one surface and a flow path for supplying cooling water to the other surface is used for every two cells. In order to prevent cooling water from leaking, an O-ring is interposed between separator plates having cooling water flow paths.
[0004]
In FIG. 11, as another sealing method for preventing leakage of gas and cooling water, a gasket 19 made of a resin or a metal plate is disposed around the electrode 1 with the same thickness as the electrode, An example in which the gap is sealed with grease 20 or an adhesive is shown. The separator plates having the cooling water flow path are similarly sealed with grease or an adhesive.
In FIG. 12, an electrode electrolyte assembly (MEA) in which an electrode is made the same size as a polymer electrolyte membrane and joined to the electrolyte membrane is laminated with a separator plate, and a resin 21 having a sealing effect in advance on a portion that requires gas sealing. It is an example using what was soaked and solidified. This solidified resin maintains the gas sealing property between the separator plate.
[0005]
Many fuel cells have a laminated structure in which a large number of unit cells having the above-described structure are stacked. During operation of the fuel cell, heat is generated as power is generated. In the laminated battery, since the cooling plate is provided for each single cell or two cells, the generated heat energy can be used in the form of hot water or the like while keeping the battery temperature constant. The cooling plate generally has a structure in which a heat medium such as cooling water flows through a thin metal plate. In addition, as described above, there is a cooling plate obtained by processing a flow path on the back surface of the separator plate constituting the unit cell, that is, the surface on which the cooling water is desired to flow. At that time, an O-ring or gasket for sealing a heat medium such as cooling water is also required. However, with this seal, it is necessary to ensure sufficient conductivity between the upper and lower sides of the cooling plate by completely crushing the O-ring. There is.
[0006]
In such a laminated battery, an internal manifold type in which a gas supply hole and a gas discharge hole to each unit cell, called a manifold, and a cooling water supply / discharge hole are secured inside the laminated battery is generally used. However, when the battery is operated using the reformed gas, the CO concentration increases in the downstream area of the fuel gas flow path of each battery. As a result, the temperature decreases due to electrode poisoning, and the decrease in temperature further increases the electrode poisoning. May be promoted. In order to alleviate such a phenomenon of battery performance degradation, the external manifold type has been reviewed as a structure that can take as wide a gap as possible between the supply and discharge portions of the gas from the manifold to each single cell.
[0007]
In any case, it is necessary to stack a large number of single cells including the cooling unit in one direction, arrange two end plates at both ends, and fix the two end plates with a fastening rod. As a tightening method, it is desirable to tighten the cells as uniformly as possible in the plane. From the viewpoint of mechanical strength, a metal material such as stainless steel is usually used for the end plate and the fastening rod. These end plates and fastening rods and the laminated battery are electrically insulated by an insulating plate or the like, and have a structure in which current does not leak outside through the end plates. As for the fastening rod, an improved system has also been proposed in which it passes through a through hole inside the separator, or the whole laminated battery is fastened with a metal belt over the end plate.
Further, in any of the sealing methods shown in FIGS. 10 to 12, a constant tightening pressure is necessary to maintain the sealing performance, and a screw spring or a disc spring is inserted between the fastening rod and the end plate. The configuration is adopted. In addition, the tightening pressure ensures electrical contact between battery constituent members such as a separator, an electrode, and an electrolyte membrane.
[0008]
[Problems to be solved by the invention]
In order to seal a gas such as hydrogen gas or air, a method of disposing a sealing material or an O-ring around the electrode requires a considerable surface pressure. Therefore, a structure is adopted in which the sealing effect is maintained by sandwiching the sealing material and the sealing portion between the upper and lower separator plates, and it is necessary to constantly apply a relatively large tightening force. For this reason, a fastening mechanism such as an end plate or a fastening rod tends to be long, which is a problem for reducing the weight of the whole battery from the viewpoint of weight.
In addition, since pressure is applied to the seal part and the electrode part for a long period of time, the constituent members are distorted, and as a result, the surface pressure required for the seal part and the electrode is reduced. Thus, a configuration is adopted in which a spring is installed at the end of the tightening rod and fastened. For this reason, it was an obstacle to miniaturization.
[0009]
[Means for Solving the Problems]
To solve the above problems, a polymer electrolyte fuel cell of the present invention is to provide a solid polymer electrolyte membrane, a pair of electrodes sandwiching the electrolyte membrane, one on the fuel gas before Symbol electrodes, said electrodes a other in the polymer electrolyte fuel cell unit cells equipped and stacking a plurality of means for supplying oxidant gas, and the end plate for pressing the both end surfaces of the cell stack, fastening the end plates A spring having a fastening member composed of a band-shaped band, an auxiliary plate having a spring for applying a fastening force to the fastening member and the end plate, and an auxiliary plate having a bolt , the spring having a dish-like shape A recess is provided in each of the peripheral edge of the auxiliary plate having the spring and the peripheral edge of the auxiliary plate having the bolt, and the auxiliary having the spring at the end of the fastening member. Wherein the convex portions respectively engaging the recesses formed on the support plate having the recess and the bolt is provided to the rate are provided.
The solid polymer fuel cell according to the present invention includes a solid polymer electrolyte membrane, a pair of electrodes sandwiching the electrolyte membrane, a fuel gas supplied to one of the electrodes, and an oxidant gas to the other of the electrodes A polymer electrolyte fuel cell in which a plurality of unit cells are provided, each of which includes an end plate that holds both end surfaces of the stacked battery, and a band-shaped band that fastens the end plates A member, an auxiliary plate having a spring for applying a fastening force to the fastening member and the end plate, and an auxiliary plate having a bolt, and the fastening member is divided into a plurality of parts, and the spring is provided. Concave portions are provided in the peripheral portion of the auxiliary plate and the peripheral portion of the auxiliary plate having the bolt, respectively, and the end portion of the fastening member is provided in the auxiliary plate having the spring. Wherein the convex portions respectively engaging in the recess provided in the parts and the auxiliary plate having the bolt is provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
<< Reference Form 1 >>
The fastening structure of the fuel cell in this Reference mode shown in FIGS.
Reference numeral 30 denotes a unit cell stack. End plates 31 and 32 are arranged above and below the laminate 30. The unit cell stack 30 having the output terminals 40 and 41 and the end plates 31 and 32 are not particularly illustrated, but are electrically insulated by an insulating means. The end plate 31, the battery stack 30 and the end plate 32 are fastened at four locations. That is, the fastening member 39 formed of a band-shaped band surrounding them, the auxiliary plate 33 to which the end of the band is fixed, and the convex portion 37 provided corresponding to the concave portion 36 provided on the bottom surface of the end plate 32 are dish-shaped. The battery stack 30 and the end plates 31 and 32 are fastened by the auxiliary plate 34 to which the spring 38 is attached and the bolt 35 screwed into the screw hole provided in the auxiliary plate 33.
When the bolt 35 is screwed into the auxiliary plate 33, the auxiliary plate 33 moves in a direction away from the end plate 31, and thus the auxiliary plate 34 moves in a direction in which the spring 38 is compressed by the band 39. As a result, the laminate 30 is tightened via the end plate, and a necessary surface pressure is applied to the seal portion and the electrode. Reference numerals 42, 43, and 44 denote a gas supply port and a cooling water supply port for supplying gas to the electrode. These discharge ports are provided on the lower surface opposite to the side having the supply ports.
[0011]
<< Embodiment 1 >>
The fuel cell fastening structure in the present embodiment is shown in FIGS.
50 represents a laminate of unit cells. End plates 51 and 52 are arranged above and below the laminate 50. An auxiliary plate 53 in which a bolt 55 is screwed into a screw hole is provided on the end plate 51, and a plate 57 is provided below the end plate 52 in correspondence with a concave portion 56 provided on the bottom surface of the end plate 52. Auxiliary plates 54 fitted with a spring 58 are respectively arranged. Auxiliary plates 53 and 54 are connected by a fastening member made up of a band 59 provided with a convex portion that engages with a concave portion 61 provided on the peripheral edge portion thereof, and bolts 55 are screwed into the auxiliary plate 53. As a result, the spring 57 is compressed, whereby the laminated body 50 is tightened via the end plates 51 and 52, and a necessary surface pressure is applied to the seal portion and the electrode. In this example, the output terminals 62 and 63 are arranged above and below the battery. A manifold 64 provided with a gas supply port and a cooling water supply port for supplying gas to the electrode, and a manifold 65 provided with a gas discharge port and a cooling water discharge port are attached to the side surface of the battery.
[0012]
<< Embodiment 2 >>
FIG. 7 shows a fastening structure of the fuel cell in the present embodiment.
In the first embodiment, two sets of fastening members are used, and each set of auxiliary plate 53 is tightened with two sets of bolts. However, in this embodiment, four sets of fastening members are used and each set of auxiliary members 53 is supported. The plate 53a has the same structure as that of the first embodiment except that the plate 53a is fastened with a set of bolts.
[0013]
【Example】
Examples of the present invention will be described below.
<< Reference Example 1 >>
Carbon powder having a particle size of several microns or less was immersed in a chloroplatinic acid aqueous solution, and a platinum catalyst was supported on the surface of the carbon powder by reduction treatment. At this time, the weight ratio of carbon to supported platinum was 1: 1. Subsequently, the platinum-supported carbon powder was dispersed in a polymer electrolyte alcohol solution to form a slurry.
On the other hand, a carbon paper having a thickness of 400 microns serving as an electrode was impregnated with an aqueous dispersion of fluororesin (Neoflon ND1 manufactured by Daikin Industries, Ltd.), dried, and then heat treated at 400 ° C. for 30 minutes to impart water repellency. .
[0014]
As shown in FIG. 8, the catalyst layer 2 was formed by uniformly applying the slurry containing the carbon powder to one surface of the carbon paper electrode 1 subjected to the water repellent treatment. The two carbon paper electrodes 1 were superposed with the surface on which the catalyst layer was formed facing inward and the solid polymer electrolyte membrane 3 sandwiched therebetween, and then dried to obtain an electrode electrolyte assembly (MEA). The two carbon paper electrodes 1 were 10 cm in length and width, and were placed in the center of the polymer electrolyte membrane 3 having a length and width that were slightly larger than 12 cm. The MEA was sandwiched between carbon separator plates 4 having airtightness from both sides to constitute a unit cell.
The separator plate 4 has a thickness of 4 mm, and a number of gas flow passages 5 having a width of 2 mm and a depth of 1 mm are engraved on the surface thereof, and a gas manifold hole 6 and a manifold of cooling water are formed on the periphery thereof. Hole 7 was provided. Further, when the MEA was sandwiched between separator plates, a polyethylene terephthalate (PET) sheet 8 having the same outer dimensions as the carbon separator plate was disposed around the electrode 1. This PET sheet is hard and does not have a sealing property, but was used as a spacer between the carbon separator plate 4 and the electrolyte membrane 3. After stacking two cells of such a single cell, a separator plate having a cooling flow path through which cooling water flows was stacked, and this pattern was repeatedly stacked. No sealing O-ring was used between separator plates having cooling channels.
50 cells of such a battery structural unit were laminated, and a laminated body was configured by arranging a metal current collector plate and an insulating plate made of an electrical insulating material at both ends.
[0015]
End plates were arranged above and below this laminate to provide the fastening structure of Reference Embodiment 1 described with reference to FIGS. In other words, a structure in which a fastening force is applied by four metal (SUS304-CSP) bands 39 having a thickness of 1 mm and a width of 22 mm, end plates 31 and 32, auxiliary plates 33 and 34, and a disc spring 38 is provided. The spring constant of the spring 38 was 500 kgf / mm, compressed by 0.8 mm, and a fastening pressure of 400 kg was applied per location, and the fastening pressure during assembly was 13 kgf / cm ² . When the pressure distribution of the separator plate was examined using pressure sensitive paper, it was confirmed that the pressure distribution was uniform over the entire surface. According to the present embodiment, compared to a conventional method in which a rod is arranged outside the separator plate to give a fastening force, the fastening force can be applied from the inside of the separator plate, so that the deformation of the end plate is drastically reduced. Therefore, the thickness of the end plate can be 5 mm or less.
[0016]
Example 1
In Reference Example 1, a PET sheet spacer was arranged around the electrode as the MEA structure, but the following structure was further attempted. That is, the carbon paper electrode on which the PET sheet is discarded and the catalyst layer is applied has the same outer dimensions as the carbon separator plate, and thus the electrode end portion is exposed on the side surface of the battery when laminated. As the carbon separator plate at this time, an external manifold type as shown in FIG. 9 was used. That is, the separator plate 4a used for every two cells has the cooling water flow path 22 and its inlet / outlet 12 on one side and the fuel gas or oxidant gas, for example, the fuel gas flow path and its inlet / outlet 10 on the other side. . The separator plate 4b is disposed in contact with the counter electrode of the electrode that contacts the surface having the gas inlet / outlet port 10 of the separator plate 4a. The separator plate 4b is provided with an oxidant gas flow path 5 and its inlet / outlet port 11 on the surface in contact with the counter electrode, and a fuel gas flow path and its inlet / outlet port 10 on the opposite surface. Further, the separator plate 4c laminated with the separator plate 4b through the unit cell is provided with the oxidant gas flow path 5 and its inlet / outlet port 11 on one surface, and the cooling water flow path and The doorway 12 is provided.
A manifold for supplying fuel gas, oxidant gas and cooling water is disposed on one side surface of the unit cell stack and the gas inlet / outlet ports 10 and 11 and the cooling water inlet / outlet, respectively. Manifolds for discharging the fuel gas, the oxidant gas and the cooling water from the gas inlets 10 and 11 and the cooling water inlet and outlet, respectively, are arranged.
[0017]
End plates are arranged above and below the laminate having the above battery configuration, and the fastening structure of the first embodiment described with reference to FIGS. That is, the structure is such that a fastening force is applied by two metal (SUS304-CSP) bands 59 having a thickness of 1 mm and a width of 75 mm, end plates 51 and 52, auxiliary plates 53 and 54, disc springs 58, and bolts 55. The spring constant of the spring 58 was 500 kgf / mm, compressed by 0.8 mm, and a fastening pressure of 400 kg per place was applied, so that the fastening pressure during assembly was 13 kgf / cm ² . In this embodiment, the claw 60 is joined to the end of the band 59 by welding so that it can be attached and detached. Therefore, the assemblability is improved as compared with the band structure of the reference example 1.
[0018]
Example 2
End plates are arranged above and below the laminate of the battery configuration of the type of Example 1 , and the fastening structure of the second embodiment described with reference to FIG. 7 is obtained. That is, the structure is such that four metal (SUS304-CSP) bands 53a having a thickness of 1 mm and a width of 75 mm, end plates 51 and 52, auxiliary plates 53 and 54, disc springs 58, and bolts 55 are used to give a fastening force. The spring constant of the spring 58 was 500 kgf / mm, compressed by 0.8 mm, and a fastening pressure of 400 kg per place was applied, so that the fastening pressure during assembly was 13 kgf / cm ² . Furthermore, it was set as the structure which divides the fastening plate of Example 1 into two. In Example 1 , since it was tightened with four bolts for one tightening plate, even if the mechanical accuracy of the band was poor, the four bolts were not equally loaded. On the other hand, in the present embodiment, since it is configured to be tightened with two bolts with respect to one tightening plate, the load can be applied evenly. When the pressure distribution of the separator plate was examined using pressure sensitive paper, it was confirmed that the pressure distribution was uniform over the entire surface.
In this embodiment, the bolt-side fastening plate is divided into two parts, but the same effect can be obtained even if the spring-side fastening plate is divided into two parts.
[0019]
【The invention's effect】
According to the present invention, the fastening mechanism such as the end plate and the fastening rod can be reduced in size and weight, and the weight of the entire battery can be reduced.
[Brief description of the drawings]
FIG. 1 is a plan view of a polymer electrolyte fuel cell according to a reference embodiment of the present invention.
FIG. 2 is a front view of the battery.
3 is a cross-sectional view taken along line III-III ′ of FIG.
4 is a plan view of a solid polymer electrolyte fuel cell in the implementation of the invention.
FIG. 5 is a front view of the battery.
6 is a cross-sectional view taken along line VI-VI ′ of FIG.
FIG. 7 is a plan view of a polymer electrolyte fuel cell according to another embodiment of the present invention.
FIG. 8 is a perspective view in which a part of a cell member of a polymer electrolyte fuel cell according to an embodiment of the present invention is cut away.
FIG. 9 is a perspective view of a separator plate according to another embodiment of the present invention.
FIG. 10 is a cross-sectional view of a main part showing a configuration example of a battery member of a polymer electrolyte fuel cell.
FIG. 11 is a cross-sectional view of the main part showing another configuration example of the battery member of the solid polymer fuel cell.
FIG. 12 is a cross-sectional view of the main part showing still another configuration example of the battery member of the polymer electrolyte fuel cell.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electrode 2 Catalyst layer 3 Solid polymer electrolyte membrane 4 Separator plate 5 Gas flow path 6 Gas manifold hole 7 Cooling water manifold hole 30, 50 Laminate 31, 32, 51, 52 End plate 33, 34, 53, 54 Auxiliary plate 35, 55 Bolt 36, 56 Concave 37, 57 Convex 38, 58 Spring 39, 59 Band 40, 41, 62, 63 Output terminal

Claims (2)

More and the solid polymer electrolyte membrane, a pair of electrodes sandwiching the electrolyte membrane, while the fuel gas is supplied to the pre-Symbol electrodes, the other to the unit cell and means for supplying an oxidant gas in the electrode It is a polymer electrolyte fuel cell that is individually stacked,
An end plate for holding both end faces of the laminated battery, a fastening member comprising a band-like band for fastening the both end plates, an auxiliary plate having a spring for applying a fastening force to the fastening member and the end plate, and a bolt ; and a has an auxiliary plate, said spring Ri Banedea with dish-shaped form, the peripheral edge portion and each concave portion to the peripheral portion of the auxiliary plate having the bolt of the auxiliary plate having the spring is arranged The end portion of the fastening member is provided with a convex portion that engages with the concave portion provided in the auxiliary plate having the spring and the concave portion provided in the auxiliary plate having the bolt, respectively. A solid polymer fuel cell. More and the solid polymer electrolyte membrane, a pair of electrodes sandwiching the electrolyte membrane, while the fuel gas is supplied to the pre-Symbol electrodes, the other to the unit cell and means for supplying an oxidant gas in the electrode It is a polymer electrolyte fuel cell in which individual layers are laminated,
An end plate for holding both end faces of the laminated battery, a fastening member comprising a band-like band for fastening the both end plates, an auxiliary plate having a spring for applying a fastening force to the fastening member and the end plate, and a bolt The fastening member is divided into a plurality of portions, and a recess is provided in each of a peripheral portion of the auxiliary plate having the spring and a peripheral portion of the auxiliary plate having the bolt. The end of the member is provided with a convex portion that engages with the concave portion provided in the auxiliary plate having the spring and the concave portion provided in the auxiliary plate having the bolt, respectively. Solid polymer fuel cell .

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