JPH05251097A - Solid polymer electrolyte fuel cell - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a solid polymer electrolyte fuel cell having excellent output stability by preventing retention and clogging of condensed water in gas flow channels. [Structure] Gas flow groove 15 through which a reaction gas passes through a separator plate
In addition, the width of the gas flow groove 15 is at least 1.5 mm at least at the downstream portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer electrolyte fuel cell, and more particularly to a gas passage groove of a separator plate for supplying a reaction gas to electrodes.

[0002]

2. Description of the Related Art A solid polymer electrolyte fuel cell is formed by disposing an anode and a cathode on two main surfaces of a solid polymer electrolyte membrane. Each electrode of the anode or the cathode has an electrode catalyst provided on an electrode base material. The solid polymer electrolyte membrane uses a polystyrene cation exchange membrane with sulfonic acid groups as the cation conductive membrane, a mixed membrane of fluorocarbon sulfonic acid and polyvinylidene fluoride, or trifluoroethylene grafted to the fluorocarbon matrix. However, recently, a perfluorocarbon sulfonic acid membrane has been used to extend the life of a fuel cell.

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

At the anode, the reaction of the formula (1) occurs. H ₂ = 2H ⁺ + 2e (1) At the cathode, the reaction of the formula (2) occurs. 1 / 2O ₂ + 2H ⁺ + 2e = H ₂ O (2) That is, at the anode, hydrogen supplied from the outside of the system produces protons and electrons. The generated protons move in the ion exchange membrane toward the cathode, 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 protons moving from the anode in the ion exchange membrane and electrons moving from the external circuit to generate water.

FIG. 3 is a plan view showing a unit cell of a conventional solid polymer electrolyte fuel cell. The anode 2 and the cathode 3 are laminated in contact with both main surfaces of the solid polymer electrolyte membrane 1 having a thickness of 100 μm. The thickness of the electrode is 300 μm.
As described above, the electrode is formed by disposing the electrode catalyst layer on the electrode base material, but this electrode catalyst layer is generally composed of a fine particulate platinum catalyst and a fluororesin having water repellency, The three-phase interface and pores for maintaining efficient diffusion of the reaction gas are sufficiently formed. The electrode base material supports the catalyst layer.

A pair of separator plates 5 for guiding the reaction gas from the outside and supplying it to the anode or the cathode are provided outside the solid polymer electrolyte membrane where the electrodes are arranged. The separator plate is a gas impermeable plate having a gas flow groove 4 for guiding the reaction gas to one main surface thereof. The gas flow groove has a depth of 1 mm and a width of 1 mm. FIG. 4 is a side view showing a stack of a conventional solid polymer electrolyte fuel cell.

The stacked unit cells 6 are cooled by the cooling plate 7 every three sheets. The current collector plate 8 takes out the current of the battery assembly. The battery assembly is assembled using the tightening plate 10 and the tightening bolts 11. Insulation plate 9 is collector plate 8
And the tightening plate 10 is electrically insulated. The reaction gas flows vertically in the unit cell. 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.
It is operated at the temperature of. The voltage generated by this unit cell is 1V
Because of the following, in practice, in order to increase the voltage, a plurality of the unit cells are stacked in series and used as a stack.

In a fuel cell, a heat quantity generally equivalent to generated electric power is generated as heat, and this heat causes a temperature distribution in the stack in which a large number of unit cells are stacked. Therefore, in the stack, a cooling plate is built in so that the temperature of the stack becomes as uniform as possible in the plane direction and the stacking direction of the unit cells. Here, water, air or the like is generally used as the cooling medium. The cooling plate is cooled by supplying a cooling medium to remove excess heat.

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 1 which is the electrolyte holding layer, and the membrane functions as a proton conductive electrolyte. .. Therefore, in order to keep the power generation efficiency of the solid polymer electrolyte fuel cell high, it is necessary to keep the water content of the membrane saturated. In order to prevent the membrane from drying and maintain power generation efficiency,
Water vapor is added to the reaction gas to suppress evaporation of water from the membrane into the gas.

[0010]

As described above, in the power generation of the fuel cell, water is produced as a reaction product, and this produced water is discharged out of the fuel cell together with the surplus reaction gas. Therefore, the amount of water contained in the gas can be distributed in the flow direction of the oxidizing gas in the unit cell. That is, the oxidant gas is
In the downstream portion (outlet side) of the gas flow with respect to the upstream portion (inlet side) of the gas flow in the unit cell, the amount of water increases by an amount corresponding to the water generated by the cathode reaction. Therefore, when the supplied gas is humidified to a saturated state and supplied to the solid polymer electrolyte fuel cell, the gas on the outlet side contains supersaturated water vapor. As a result, water corresponding to supersaturation condenses on the gas outlet side. The condensed water blocks the gas passage and hinders the gas flow in the gas flow groove. As a result, the supply of the reaction gas to the electrodes becomes insufficient, resulting in a decrease in the unit cell output. In order to prevent this, promptly discharging condensed water to the outside is extremely important in operation. Similar problems occur with fuel gas. The hydrogen gas in the fuel gas is consumed as a result of the electrode reaction at the anode, so that the humidified water vapor in the fuel gas becomes supersaturated and condensed near the outlet.

The present invention has been made in view of the above-mentioned points, and an object thereof is to provide a solid polymer electrolyte fuel cell which is excellent in output stability by preventing retention blockage of condensed water in a gas flow groove. is there.

[0012]

According to the present invention, there is provided a solid polymer electrolyte membrane, both anode and cathode electrodes, and a separator plate. The solid polymer electrolyte membrane contains water. Protons are diffused through the membrane, the anode and cathode electrodes are arranged opposite to each other via the solid polymer electrolyte membrane, and the separator plate is provided with a plurality of gas passages through which both reaction gases of fuel gas and oxidant gas flow. A flow groove is provided on one of the main surfaces to sandwich the solid polymer electrolyte membrane on which the electrodes are arranged, and to supply the fuel gas and the oxidant gas to the anode and the cathode, respectively. At least the downstream portion of the flow groove has a width of 1.5 mm or more.

[0013]

In the present invention, the size of the gas flow groove required for promptly discharging the condensed water in the unit cell to the outside is defined.
When a groove having a size larger than the groove size defined in the present invention is used as the gas flow groove, condensed water can flow down the gas flow groove by gravity.

[0014]

1 shows a separator plate of a solid polymer electrolyte fuel cell according to an embodiment of the present invention. FIG. 1 (a) is a plan view of the separator plate, and FIG. 1 (b) is a separator plate A.
A sectional view and FIG. 1C are BB sectional views of the separator plate. The reaction gas supplied from the outside is supplied from the manifold 13 to the separator plate, and is distributed and supplied from the manifold 14 inside the separator plate to the plurality of gas flow grooves 15. Further, the reaction gas is collected by the manifold 16 in the separator plate and discharged from the manifold 17 to the outside. Here, the gas flow groove 15
The groove width of the upstream part is narrower than that of the downstream part. The width of the upstream part is 1 mm and the width of the downstream part is 3 m
m. The separator plate was manufactured using carbon. The separator plate manifold 14 and the separator manifold 16 have the same depth, and they are deeper than the depth of the gas flow groove 15.

FIG. 2 shows the time characteristic (characteristic (a)) of the output of the solid polymer electrolyte fuel cell according to the embodiment of the present invention in comparison with the conventional time characteristic (characteristic (b)). It is a diagram. The solid polymer electrolyte fuel cell has an output of 0.
It was operated at 3 W / cm ² . The flow rate of the oxidizing gas is 50 to 100 l / min. And the linear velocity of gas is 50
Or 100 cm / s. The flow rate of the fuel gas is 11 to 13 l / min. And its linear velocity is 2
It was 5 to 40 cm / s. The temperature of the solid polymer electrolyte fuel cell was 70 to 80 ° C. Under these experimental conditions, it can be seen that the condensed water does not stay or block in the gas flow groove, and stable output operation is possible.
Similar results were obtained when the width of the downstream portion of the gas flow groove 15 was 1.5 mm.

The downstream portion of the gas flow groove is a region where the reaction gas flowing in the gas flow groove reaches supersaturation. The region where this supersaturation is reached is easily determined by the supply amount of the reaction gas, the humidification amount of the reaction gas, the operating temperature of the solid polymer electrolyte fuel cell, the total pressure of the supply gas, the load amount of the solid polymer electrolyte fuel cell, etc. can do. In the conventional solid polymer electrolyte fuel cell, the width of the gas flow groove is small, and condensed water stays inside the gas flow groove, obstructing the passage of the reaction gas, and the output of the cell changes periodically. ing.

In the above embodiment, the width is different between the upstream portion and the downstream portion of the gas flow groove, but the same result is obtained when the width is 1.5 mm or more. Further, as the material, metal such as titanium or tantalum may be used instead of carbon.

[0018]

According to the present invention, a solid polymer electrolyte membrane, both anode and cathode electrodes, and a separator plate are provided. The solid polymer electrolyte membrane contains water so that protons diffuse in the membrane. Both the anode and cathode electrodes are arranged to face each other with a solid polymer electrolyte membrane in between, and the separator plate has a plurality of gas flow grooves through which both reaction gases of a fuel gas and an oxidant gas flow, and its main surface is one side. In preparation for this, the solid polymer electrolyte membrane having the electrodes is sandwiched, and the fuel gas and the oxidant gas are supplied to the anode and the cathode, respectively. At this time, at least the downstream portion of the gas flow groove is Since it has a width of 1.5 mm or more, the condensed water does not stay in the gas flow grooves of the separator plate and is quickly discharged. As a result, a solid polymer electrolyte fuel cell with stable output can be obtained.

[Brief description of drawings]

1 shows a separator plate of a solid polymer electrolyte fuel cell according to an embodiment of the present invention, FIG. 1 (a) is a plan view of the separator plate, FIG. 1 (b) is a sectional view taken along the line AA of the separator plate,
FIG. 1C is a BB cross-sectional view of the separator plate.

FIG. 2 is a diagram showing the time characteristic (characteristic (a)) of the output of a single cell of the solid polymer electrolyte fuel cell according to the embodiment of the present invention in comparison with the conventional time characteristic (characteristic (b)).

FIG. 3 is a plan view showing a unit cell of a conventional solid polymer electrolyte fuel cell.

FIG. 4 is a side view showing a stack of a conventional solid polymer electrolyte fuel cell.

[Explanation of symbols]

 1 Solid Polymer Electrolyte Membrane 2 Anode 3 Cathode 4 Gas Flow Groove 5 Separator Plate 6 Single Cell 7 Cooling Plate 8 Current Collector 9 Insulating Plate 10 Clamping Plate 11 Clamping Bolt 12 Stack 13 Manifold 14 Manifold in Separator Plate 15 Gas Flowing Groove 16 Manifold in separator plate 17 Manifold

Claims (4)

[Claims] 1. A solid polymer electrolyte membrane, both anode and cathode electrodes, and a separator plate, wherein the solid polymer electrolyte membrane contains water so that protons diffuse in the membrane, Both electrodes are arranged so as to face each other with the solid polymer electrolyte membrane interposed therebetween, and the separator plate is provided with a plurality of gas flow grooves through which both reaction gases of the fuel gas and the oxidant gas flow, on one main surface thereof,
The solid polymer electrolyte membrane having the electrodes is sandwiched and fuel gas and oxidant gas are supplied to the anode and the cathode, respectively. At this time, at least the downstream portion of the gas flow groove is 1.5 mm or more. A solid polymer electrolyte fuel cell having a width of 2. The solid polymer electrolyte fuel cell according to claim 1, wherein the separator plate is made of carbon. 3. The solid polymer electrolyte fuel cell according to claim 1, wherein the separator plate is made of metal. 4. The solid polymer electrolyte fuel cell according to claim 1, wherein the gas flow channels are arranged in a vertical direction.