JP3149716B2 - Solid polymer electrolyte fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a solid polymer electrolyte fuel cell, and more particularly to a structure for stacking and cooling a stack.

[0002]

2. Description of the Related Art A solid polymer electrolyte fuel cell is formed by disposing an anode and a cathode as electrodes on two main surfaces of a solid polymer electrolyte membrane. Each of the anode and cathode electrodes has an electrode catalyst layer on an electrode substrate. Solid polymer electrolyte membranes (abbreviated as solid polymer membranes) use a polystyrene-based cation exchange membrane having sulfonic acid groups as the cation conductive membrane, a mixed membrane of fluorocarbon sulfonic acid and polyvinylidene fluoride, or There are known ones obtained by grafting trifluoroethylene onto a fluorocarbon matrix, but recently, those using a perfluorocarbon sulfonic acid membrane to extend the life of a fuel cell have come to be known.

[0003] A solid polymer electrolyte membrane has a proton (hydrogen ion) exchange group in the molecule, exhibits a specific resistance of 20 Ω · cm or less at room temperature when saturated with water, and functions as a proton conductive electrolyte. The saturated water content changes reversibly with temperature. The electrode substrate is a porous body and functions as a reactant gas supply unit or a reactant gas discharge unit of the fuel cell and a current collector. At the anode (fuel electrode) or cathode (air electrode), a three-phase interface is formed and an electrochemical reaction occurs.

At the anode, the reaction of the formula (1) takes place. H ₂ = 2H ⁺ + 2e (1) At the cathode, the reaction of equation (2) occurs. 1 / 2O ₂ + 2H ⁺ + 2e = H ₂ O (2) That is, at the anode, hydrogen supplied from outside the system generates protons and electrons. The generated protons move toward the cathode in the ion exchange membrane, and the electrons move to the cathode through an external circuit. On the other hand, in the cathode, oxygen supplied from the outside of the system reacts with the protons traveling from the anode through the ion exchange membrane and the electrons traveling from the external circuit to produce water.

FIG. 4 is a sectional view showing a single cell of a conventional solid polymer electrolyte fuel cell. The anode 1B and the cathode 1C are stacked in contact with both main surfaces of the solid polymer electrolyte membrane 1A having a thickness of 100 μm to form the solid polymer membrane / electrode assembly 1. The thickness of the electrode is 300 μm. The electrode is configured by arranging an electrode catalyst layer on the electrode substrate as described above, but this electrode catalyst layer is generally formed of a fine particulate platinum catalyst and a fluororesin having water repellency to water,
Sufficient pores are formed to maintain the three-phase interface and efficient diffusion of the reaction gas. An electrode substrate supports the catalyst layer.

Solid polymer electrolyte membrane 1A on which electrodes are arranged
A pair of separators 2A and 2B made of, for example, carbon are provided on the outside of the substrate 2 to supply a reaction gas from the outside to the anode 1B or the cathode 1C. Separator 2
Reference numerals A and 2B denote gas impermeable plates provided with a fuel gas chamber 3A or an oxidizing gas chamber 3B for guiding a reaction gas to the main surface.
The dimension of the fuel gas chamber 3A or the oxidizing gas chamber 3B is 1 depth.
mm and a width of 1 mm. The separators 2A and 2B are provided with a fuel gas supply hole 31, an oxidant gas supply hole 32, a fuel gas discharge hole 34, and an oxidant gas discharge hole 35. The solid polymer membrane / electrode assembly 1 is sandwiched between separators 2A and 2B via a gas seal 5.
Is configured. The gas seal 5 has a cut 33 for selectively supplying and discharging a fuel gas and an oxidizing gas to and from the solid polymer membrane / electrode assembly 1.

FIG. 5 is a perspective view showing a conventional fastening plate.
The fastening plate 10 is a solid plate made of metal and includes a through hole 16 through which a fastening bolt is inserted, a reaction gas supply hole 14, and a reaction gas discharge hole 15. The reaction gas supply hole 14 is a seal groove 14A.
And a mounting screw 14B for a gas pipe (not shown).
The reaction gas discharge hole 15 has a seal groove 15A and a screw 15B for attaching a gas pipe (not shown).

FIG. 6 is a perspective view showing a conventional solid polymer electrolyte fuel cell. A plurality of single cells 6 are stacked to form a single cell aggregate, and a current collector 8 extracts the current of the single cell aggregate. The electric insulating plate 9 is composed of a single cell assembly and a fastening plate 10.
Insulate. The battery assembly includes a fastening plate 10 and a fastening bolt 1
1, the fastener 13 and the disc spring 12 are assembled. The reaction gas flows in the single cell 6 in the vertical direction.

The operating temperature of the solid polymer electrolyte fuel cell is usually 50 to 100 ° C. in order to reduce the electric resistance of the solid polymer electrolyte membrane and increase the power generation efficiency. Since the voltage generated by this single cell is 1 V or less,
Practically, in order to increase the voltage, a plurality of the single cells are stacked in series and used as a stack. In a fuel cell, generally, a heat amount substantially corresponding to the generated electric power is generated as heat, and this heat causes a temperature distribution in the stack in which many single cells are stacked. So in the stack,
A cooling plate is incorporated to make the temperature of the stack as uniform as possible in the plane direction and the stacking direction of the single cells. Here, water, air or the like is generally used as a cooling medium. The cooling plate cools by removing excess heat by supplying a cooling medium.

As described above, in the solid polymer electrolyte fuel cell, the specific resistance of the membrane is reduced by saturating the solid polymer electrolyte membrane 1A with water, and the membrane functions as a proton conductive electrolyte. Therefore, in order to keep the power generation efficiency of the polymer electrolyte fuel cell high, it is necessary to maintain the water-containing state of the membrane in a saturated state. In order to prevent drying of the film and maintain power generation efficiency, steam is added to the reaction gas to suppress evaporation of water from the film into the gas.

[0011]

However, in such a conventional solid polymer electrolyte fuel cell, the fastening plate is the heaviest component, and the weight of the fastening plate is about the total weight of the entire solid polymer electrolyte fuel cell. Accounts for 30-50%.
It is expected that the weight of the fastening plate will further increase in the future as the power generation area increases and the number of stacked single cells increases. If the weight of the fastening plate is large, it is difficult to assemble the solid polymer electrolyte fuel cell, and the efficiency of product transportation is reduced.

Further, the fastening plate acts as a radiator of the polymer electrolyte fuel cell, so that the temperature of the single cell in contact with the fastening plate is reduced, and the power generation efficiency of the single cell in contact with the fastening plate is reduced. Further, in the conventional fastening plate, the reaction gas is cooled when the reaction gas flows through the reaction gas supply hole 14 and the reaction gas discharge hole 15 penetrating the fastening plate. There is a problem that water droplets are generated in the liquid crystal 15 and flow of the reaction gas is deteriorated, and as a result, the power generation efficiency of the polymer electrolyte fuel cell is reduced.

The present invention has been made in view of the above points, and an object of the present invention is to provide a polymer electrolyte fuel cell which is easy to manufacture and has excellent characteristics by reducing the weight of a fastening plate and reducing heat radiation. .

[0014]

SUMMARY OF THE INVENTION According to the present invention, there is provided a solid polymer membrane / electrode assembly comprising a solid polymer electrolyte membrane and electrodes disposed on both surfaces thereof, and a reaction gas supply hole and a reaction gas supply hole. A single cell is constituted by sandwiching between two separators having discharge holes, a plurality of the single cells are stacked between two fastening plates and fastened via fastening bolts to form a stack, and a fastening plate is formed on the stack. In a solid polymer electrolyte fuel cell that supplies a reaction gas of a fuel gas and an oxidizing gas through a fuel cell, an end plate is fixed to both main surfaces of the honeycomb plate via plate-like packings, and the honeycomb plate has a honeycomb plate. The plate supports the honeycomb body on the frame, and the plate-shaped packing and the end plate have gas communication holes and support holes communicating with each other, and the plate-shaped packing is pressed against the main surface of the honeycomb body by the end plate. Toto Gas through holes of the plate packing is achieved by a communication with the hollow portion of the honeycomb body.

[0015] In the above invention, a hollow cylindrical fitting having a locking portion locked at one end to the end plate is inserted from the support hole of one end plate into the support hole of the other end plate, It is effective that a gas pipe is attached to the end of the fitting on the side opposite to the locking portion. It is effective that the fitting is made of a fluororesin.

[0016]

The hollow portion of the honeycomb body has the effect of reducing the weight of the fastening plate and the effect of mechanical reinforcement, and also has the function of flowing gas. When a honeycomb body is used as the fastening plate, the honeycomb body is made of a thin wall, so that the heat conductivity is low and the heat retaining property by air is added, so that a fastening plate with low heat dissipation can be obtained.

When the reaction gas flows through the fitting, the fitting has a low thermal conductivity, so that the reaction gas is cooled by the fastening plate to a lesser extent than when the reaction gas flows directly through the inside of the honeycomb body. Become. Fluororesin has low thermal conductivity and is suitably used for fitting.

[0018]

Next, an embodiment of the present invention will be described with reference to the drawings. Embodiment 1 FIG. 1 is an exploded perspective view showing a fastening plate of a solid polymer electrolyte fuel cell according to an embodiment of the present invention.

The honeycomb body 17B made of aluminum is supported by welding on a frame 17A also made of aluminum to form a honeycomb plate 17. The honeycomb body 17B is manufactured by cutting a hexagonal pipe made of aluminum into a predetermined length, and bonding the obtained hollow hexagonal columns in parallel. The main surface of the honeycomb body 17B obtained by bonding is on the same plane as the opening surface of the frame 17A. The plate-like packing 18 is a plate made of ethylene propylene copolymer or nitrile rubber, and has four gas flow holes 18A and six through holes 18B. The end plate 19 is made of aluminum, and has six through holes 19B and four support holes 19A. Fastening bolts are inserted into the through holes 19B of the end plate 19 and the through holes 20B of the end plate 20. The support hole 19A is a counterbore.
The end plate 20 is made of aluminum, and has six through holes 20B and four support holes 20A. The fitting 22 has at one end a locking portion to be locked in the counterbore of the support hole 19A, a sealing groove 24 is formed in this locking portion, and a tapered screw is provided at the other end. The fitting 22 is made of fluororesin, and the support hole 1 of the end plate 19 is provided.
Starting from 9A, gas flow holes 18A in plate packing 18
Then, the hollow portion of the hollow hexagonal column constituting the honeycomb body 17B of the honeycomb plate 17 is interposed, and ends at the support hole 20A of the end plate 20. The four support holes 19A correspond to a fuel gas supply hole, an oxidant gas supply hole, a fuel gas discharge hole, and an oxidant gas discharge hole, respectively.

The end plates 19 and 20, the plate-like packing 18 and the honeycomb plate 17 are joined via an ethylene-propylene copolymer-based or nitrile rubber-based adhesive. The taper screw connects a gas pipe (not shown). The seal groove 24 is fitted with a packing (not shown) and pressed against the unit cell 6. FIG. 2 is a perspective view showing a solid polymer electrolyte fuel cell according to an embodiment of the present invention.

A plurality of unit cells 6 are stacked, and both sides of the unit cells 6 in the stacking direction are sequentially sandwiched between a pair of current collector plates 8 and a pair of electric insulating plates 9, and fittings 22 and 23 are connected to fastening plates 21. Of the unit cell 6, the current collecting plate 8, and the electrical insulating plate 9 are fastened by a pair of the fastening plates 21 via the fastening bolts 11, the fasteners 13, and the disc springs 12.

Each of the current collector plate 8 and the electric insulating plate 9 has through holes communicating with the four support holes 19A and 20A of the fastening plate 21. These through holes are provided for the fuel gas supply hole and the oxidant gas supply hole of the unit cell 6. The hole, the fuel gas discharge hole, and the oxidant gas discharge hole communicate with each other. The fastening plate 21 is lightweight because the honeycomb plate 17 is used, and improves the efficiency of fuel cell assembly and fuel cell transportation.

Since the fastening plate 21 uses the honeycomb plate 17 and has a low thermal conductivity, the fastening plate does not function as a radiator, and a single cell in contact with the fastening plate 21 is cooled by the fastening plate. Since there is no single cell, the single cell in contact with the fastening plate 21 does not cause a temperature drop and the power generation efficiency of the single cell in contact with the fastening plate is good. When the reactant gas flows through the fittings 22 and 23 made of the fluororesin, the reactant gas is less likely to be cooled by the fastening plate because the fluorine resin has a low thermal conductivity. A single cell in contact with the plate 21 is not blocked by water droplets.
This means that the reaction gas is sufficiently supplied to the single cell in contact with the fastening plate 21. Embodiment 2 FIG. 3 is a perspective view showing a fastening plate of a solid polymer electrolyte fuel cell according to another embodiment of the present invention.

No fitting is attached to the fastening plate 21. The reaction gas flows directly through the hollow hexagonal column of the honeycomb body 17B and the support holes 19A, 20B of the end plates 19, 20. The end plate 19 is provided with a seal groove 24A,
The seal groove 24A is pressed against the unit cell 6. A not-shown gas pipe mounting screw is provided in the support hole 20A of the end plate 20.

In the above-described embodiment, the hollow portion of the honeycomb body has a hexagonal prism shape. However, the present invention is not limited to this, and it is sufficient if the honeycomb body has a hollow hole such as an octagonal prism shape.

[0026]

According to the present invention, since the inside of the fastening plate has a honeycomb structure, the weight of the fastening plate is reduced, and the manufacture and transportation of the polymer electrolyte fuel cell are facilitated.
In addition, a solid polymer electrolyte fuel cell having excellent characteristics can be obtained without water droplets flowing into the single cell in contact with the fastening plate or the temperature of the single cell in contact with the fastening plate being reduced because the heat dissipation of the fastening plate is reduced. .

Further, when a fitting made of a fluororesin is attached to the fastening plate, an effect of further reducing the cooling of the reaction gas by the fastening plate can be obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a fastening plate of a polymer electrolyte fuel cell according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a solid polymer electrolyte fuel cell according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a fastening plate of a polymer electrolyte fuel cell according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a single cell of a conventional solid polymer electrolyte fuel cell.

FIG. 5 is a perspective view showing a conventional fastening plate.

FIG. 6 is a perspective view showing a conventional solid polymer electrolyte fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid polymer membrane / electrode assembly 1A Solid polymer membrane 1B Anode 1C Cathode 2A Separator 2B Separator 3A Fuel gas chamber 3B Oxidant gas chamber 6 Single cell 8 Current collecting plate 9 Electrical insulating plate 10 Fastening plate 11 Fastening bolt 12 Plate Spring 13 Fastener 14 Reaction gas supply hole 14A Seal groove 14B Mounting screw 15 Reaction gas discharge hole 15A Seal groove 15B Mounting screw 16 Through hole 17 Honeycomb plate 17A Frame 17B Honeycomb body 18 plate packing 18B Gas flow hole 19 End plate 19A Support hole 19B Through hole 20 End plate 20A Support hole 20B Through hole 21 Fastening plate 22 Fitting 23 Fitting 24 Seal groove 24A Seal groove

Claims (3)

(57) [Claims] 1. A single cell comprising a solid polymer electrolyte membrane / electrode assembly comprising a solid polymer electrolyte membrane and electrodes disposed on both surfaces thereof, sandwiched between two separators having a reaction gas supply hole and a reaction gas discharge hole. A plurality of the single cells are stacked between two fastening plates and fastened via fastening bolts to form a stack, and a reactant gas of a fuel gas and an oxidizing gas is supplied to the stack via the fastening plates. In the solid polymer electrolyte fuel cell, the fastening plate is formed by fixing end plates to both main surfaces of the honeycomb plate via plate-like packing, and the honeycomb plate here supports the honeycomb body on a frame, The plate-like packing and the end plate are provided with a gas flow hole and a support hole communicating with each other, and the plate-like packing is pressed against the main surface of the honeycomb body by the end plate and the gas flow hole of the plate-like packing is formed in the honeycomb body. of Solid polymer electrolyte fuel cell characterized in that communicating with the hollow portion. 2. The fuel cell according to claim 1, wherein a hollow cylindrical fitting having a locking portion locked at one end to the end plate is provided from a support hole of one end plate to the other end plate. A solid polymer electrolyte fuel cell, wherein the fuel cell is inserted into a support hole, and a gas pipe is attached to an end of the fitting on the side opposite to the locking portion. 3. The solid polymer electrolyte fuel cell according to claim 2, wherein the fitting is made of a fluororesin.