JPH06333581A - Solid poly electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To provide a solid polyelectrolyte fuel cell capable of reducing the collected stress added to an electrolytic film and reducing the generating frequency of breakage of the electrolytic film by the pressure difference between a fuel gas and an oxidizing agent gas. CONSTITUTION:A cell 1 for solid polyelectrolyte fuel cell is a cell for solid polyelectrolyte fuel cell using separators 2A, 2B as separator to the cell of a conventional solid polyelectrolyte fuel cell. The separator 2A has the same structure as in the conventional one, the separator 2B has recessed grooves (gas passing grooves) 61B in the positions opposed through a fuel cell 7 to a plurality of protruding bulkheads 62A possessed by the separator 2A, and protruding bulkheads 62B are formed in the middle position between the gas passing grooves 61B. Thus, the gas passing grooves 61A of the separator 2A are situated in the positions opposed to the protruding bulkheads 62B of the separator 2B through the fuel cell 7.

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 of a separator improved to reduce stress applied to a solid polymer electrolyte membrane.

[0002]

2. Description of the Related Art As fuel cells, various types of fuel cells such as solid polymer electrolyte type, phosphoric acid type, molten carbonate type, and solid oxide type are known, depending on the type of electrolyte used therein. Among them, the solid polymer electrolyte fuel cell shows a low resistivity when it is saturated with a polymer resin membrane having a proton (hydrogen ion) exchange group in the molecule, and functions as a proton conductive electrolyte. It is the fuel cell used.

FIG. 4 is a side sectional view schematically showing a unit cell of a conventional solid polymer electrolyte fuel cell in a developed state. In FIG. 4, reference numeral 7 is a fuel battery cell including an electrolyte layer 7C, a fuel electrode (also serving as an anode electrode) 7A, and an oxidant electrode (also serving as a cathode electrode) 7B. The electrolyte layer 7C is a thin solid polymer electrolyte membrane (hereinafter, may be abbreviated as PE membrane) in a rectangular shape.
It consists of The fuel electrode 7A is an electrode that is closely stacked on one main surface of the PE film 7C and receives a supply of a fuel gas (for example, hydrogen or a gas containing hydrogen at a high concentration). The oxidizer electrode 7B is a PE film 7C.
Is an electrode that is intimately stacked on the other main surface of the electrode and is supplied with an oxidizing gas (for example, air). The outer surface side of the fuel electrode 7A is one side surface 7a of the fuel cell unit 7.
The outer surface side of the oxidizer electrode 7B is the fuel cell 7
It is the other side surface 7b. The fuel electrode 7A and the oxidant electrode 7B both have respective catalyst layers containing a catalyst active material,
A porous electrode substrate that supports the catalyst layer and supplies and discharges a reaction gas (hereinafter, fuel gas and oxidant gas are collectively referred to as such) and has a function as a current collector. And the catalyst layer is placed on both main surfaces of the PE film 7C by hot pressing.

Further, 6A is made of a gas impermeable material and is disposed on one side surface 7a of the fuel cell 7 to allow a fuel gas (not shown) to flow to one side thereof and to consume unconsumed gas. A plurality of concave grooves (gas distribution grooves) 61A provided at the same intervals for discharging the hydrogen-containing fuel gas, and a convex partition wall 62A interposed between the gas distribution grooves 61A, The separators are alternately formed. 6B is disposed on the other side surface 7b side of the fuel cell unit 7 and has the same interval for discharging an oxidant gas not shown in the drawing while allowing an oxidant gas not shown to flow therethrough. A plurality of concave grooves (gas distribution grooves) 61B, and the gas distribution grooves 61B.
The convex partition walls 62B interposed between B are formed alternately with each other, and like the separator 6A, are separators made of a gas impermeable material.

The tops of the convex partition walls 62A and 62B are the side surfaces 6Aa and 6A of the separators 6A and 6B, respectively.
It is formed so as to be flush with Ba. The side surface 6Aa of the separator 6A is brought into close contact with the side surface 7a of the fuel cell 7, and the separator 6B has the side surface 6Ba.
Are closely contacted with the side surfaces 7b of the fuel battery cells 7, and the fuel battery cells 7 are sandwiched therebetween.

Further, 71 is a gas seal body which serves to prevent the reaction gas flowing in the gas flow grooves 61A and 61B of the separators 6A and 6B from leaking out of the flow passages. Peripheral portions of the separators 6A and 6B,
It is arranged in a space between the fuel cell 7 and the peripheral portion thereof. The voltage generated by one fuel battery cell 7 is 1
Since the value is as low as about [V] or less, a large number of unit cells 5 having the above-mentioned configuration are connected in series with each other through each fuel cell 7 and the separators 6A and 6B inserted therein. It is generally configured as a battery cell integrated body (hereinafter, may be abbreviated as a stack), and is generally put to practical use by increasing the voltage.

FIG. 5 is a schematic diagram showing a stack of a solid polymer electrolyte fuel cell. In FIG.
Reference numeral 8 is a stack of a plurality of unit cells 5, and current collector plates 81a and 81b for collecting direct current electricity generated in the fuel cells 7 of the plurality of unit cells 5 at both ends thereof, the unit cells 5 and a collector plate. Both sides of the laminated body in which the electric insulating plates 82a and 82b for electrically insulating the electric plates 81a and 81b from the structure, the unit cells 5, the current collecting plates 81a and 81b, and the electric insulating plates 82a and 82b are laminated. Tightening plate 83a arranged at the end,
83b and a tightening bolt 84 for applying an appropriate pressing force to the tightening plates 83a and 83b, and in addition to these, a cooling body 85 that is inserted every time a plurality of unit cells 5 are stacked. It is a polymer electrolyte fuel cell stack. In the stack 8 configured in this way, the separators 6A and 6B are arranged such that the flow direction of the reaction gas flowing through the gas flow grooves 61A and 61B is the gravity direction on the supply side as indicated by the arrow in FIG. On the upper side, the discharge side is arranged on the lower side with respect to the gravity direction.

In the fuel cell unit 7, when generating direct current electricity, which will be described later, a loss equivalent to the amount of generated electric power occurs. The role of the cooling body 85 is to remove the heat due to this loss. A coolant such as water or air (not shown) for removing heat is passed through the cooling body 85 to keep the fuel cell unit 7 at an appropriate temperature described later. Therefore,
In the stack 8 having the configuration shown in FIG. 5, the separators 6A and 6B ensure the passage of the reaction gas to be supplied to the fuel cell 7 by the gas circulation grooves 61A and 61B, and The generated direct current electricity and the heat generated in the fuel cell 7 are connected to the convex partition walls 62A, 62B.
It also plays a role of transmitting to the current collector plates 81a and 81b and the cooling body 85 via. In stack 8,
Since suppressing the electric resistance and the thermal resistance between the fuel cell 7 and the current collectors 81a and 81b and the cooling body 85 to be small improves the characteristics of the fuel cell, the electric resistance and the heat at each contact portion are improved. In order to reduce the resistance,
It is pressurized by the tightening bolt 84 so that a constant pressure is always applied. Generally, this pressure is about several kg / cm ² .

In this stack 8, a fuel gas is supplied to the fuel electrode 7A and an oxidant gas is supplied to the oxidant electrode 7B for each of the fuel electrode 7A and the oxidant electrode 7B included in the plurality of fuel cells 7. By doing so, the three-phase interface (the catalyst in the catalyst layer, the PE film, and one of the reaction gases are in contact with each other at the interface between the catalyst layer of each of the electrodes 7A and 7B and the electrolyte layer 7C made of the PE film. Interface), and direct current is generated by causing an electrochemical reaction. The catalyst layer is formed of a fine particle platinum catalyst and a fluororesin having water repellency, and by forming a large number of pores, the reaction gas is efficiently diffused up to the three-layer interface. Is maintained and a three-layer interface having a sufficiently large area is formed.

By the way, P forming the electrolyte layer 7C
As described above, the E membrane is a polymer membrane having a proton (hydrogen ion) exchange group in the molecule, and shows a resistivity of 20 [Ω · cm] or less at room temperature when it is saturated with water and exhibits a proton conductive electrolyte. It is a film that functions as. The saturated water content of this PE membrane reversibly changes with temperature. In addition,
As the PE film, at present, a perfluorosulfonic acid resin film (for example, Nafion film manufactured by DuPont, USA) is known. The electrochemical reaction that occurs at the three-phase interface formed by the electrolyte layer 7C using such a PE film, the catalyst layer, and the reaction gas is as follows.

At the anode electrode 7A, the reaction of the formula (1) occurs.

[0012]

[Equation 1]

At the cathode electrode 7B, the reaction of the formula (2) occurs.

[0014]

[Equation 2]

That is, at the anode electrode 7A, hydrogen supplied from the outside produces protons and electrons. The generated protons pass through the PE film 7C into the cathode electrode 7
The electrons move toward B and move to the cathode electrode 7B through an external electric circuit (not shown). On the other hand, at the cathode electrode 7B, oxygen supplied from the outside reacts with the protons moving from the anode electrode 7A in the PE film and the electrons moving from the external electric circuit to generate water. Thus, the fuel cell 7 obtains hydrogen and oxygen to generate direct current electricity. In such a solid polymer electrolyte fuel cell, in order to reduce the resistivity of the PE film 7C to obtain high power generation efficiency,
It is operated under a temperature condition of about 50 [° C] to 100 [° C]. Since the PE film 7C is also a film that does not allow the reaction gas such as the fuel gas and the oxidant gas to pass through, it also plays the role of preventing so-called cross leak in which the reaction gases are mixed with each other.

From the above, in order to maintain the power generation efficiency of the solid polymer electrolyte fuel cell at a high level, it is necessary to maintain the water content of the PE membrane 7C at a saturated state at the above operating temperature. In addition, conventionally, the reaction gas is humidified to increase the humidity and supply it to the fuel cell unit 7 to suppress the evaporation of water from the PE film 7C to the reaction gas, thereby reducing the PE film 7C.
It has been implemented to prevent the oil from drying out. By the way, in the fuel cell 7, as described above, water is produced as a reaction product at the time of power generation. For this,
The reaction gas in the unit cell 5 contains a large amount of water vapor on the downstream side (discharge side) with respect to the upstream side (supply side) by an amount corresponding to the reaction product water. Therefore, when the reaction gas to be supplied is saturated and humidified and then supplied to the solid polymer electrolyte fuel cell, the reaction gas on the discharge side contains supersaturated water vapor, so that the reaction gas on the discharge side corresponds to supersaturated water vapor. Will be condensed and will exist in the liquid state.
The water in the liquid state is arranged such that the gas circulation grooves 61A and 61B provided in the separators 6A and 6B are arranged such that the reaction gas supply side is above the gravity direction and the discharge side is below the gravity direction. The gas distribution grooves 61A, 61
It flows down in B by gravity and is discharged to the outside of the solid polymer electrolyte fuel cell.

Further, as the separator, in addition to the separators 6A and 6B having the above-described groove 61A or groove 61B arranged on only one side surface, the grooves of the separators adjacent to each other in the stack structure are integrally formed. By doing so, in order to rationalize the stack configuration, the gas flow groove 6
There is also known a separator in which 1A and 61B are arranged on both side surfaces thereof.

[0018]

In the solid polymer electrolyte fuel cell using the separator according to the above-mentioned conventional technique, the function of direct current power generation is sufficiently exhibited.
There are the following problems. That is, the PE film 7C, which is the electrolyte of the solid polymer electrolyte fuel cell, has the property that creep occurs when pressure is continuously applied and the film thickness thereof decreases. In particular, when the operating temperature is high, when the film contains sufficient water, when high pressure is applied to a small area, the creep progresses rapidly. As described above, the solid polymer electrolyte fuel cell is operated in a state in which the PE film 7C is sufficiently water-containing as well as the operating temperature is raised. Will be.

Further, in the conventional solid polymer electrolyte fuel cell, the convex partition walls 62A and 62B of the separator 6A and the separator 6B constituting the unit cell 5 are as shown in FIG.
As shown in the figure, the fuel cells 7 are arranged so as to face each other. As a result, the PE film 7C located at the position sandwiched by the tops of the convex partition walls 62A and 62B is pressed from both sides of the film at the tops via the fuel electrode 7A and the oxidizer electrode 7B to apply a concentrated load. Upon receiving it, creep occurs, which may reduce the film thickness. PE film 7
When the film thickness decreases in C, the tensile strength of the PE film 7C decreases at that portion, and when the fuel cell is operated for a long time, PE becomes due to the pressure difference between the fuel gas and the oxidant gas at this portion.
In some cases, the membrane 7C was damaged, making it impossible to continue the operation of the fuel cell as illustrated in FIG.

The present invention has been made in view of the above-mentioned problems of the prior art, and its object is to reduce the concentrated stress applied to the PE membrane while maintaining the high efficiency of the solid polymer electrolyte fuel cell. Another object of the present invention is to provide a solid polymer electrolyte fuel cell that can reduce the occurrence of damage to the PE membrane due to the pressure difference between the fuel gas and the oxidant gas.

[0021]

SUMMARY OF THE INVENTION In the present invention, the above-mentioned objects are as follows: 1) A fuel battery cell for receiving a supply of a fuel gas and an oxidant gas to generate DC power, and arranged on both sides of the fuel battery cell. A fuel cell having a separator having a plurality of gas flow grooves for supplying a fuel gas or an oxidant gas to the fuel cell, the fuel cell having an electrolyte layer made of a PE film and two main surfaces of the PE film. Each of the separators has an electrode arranged in close contact with each other, and each separator is adjacent to each other with a plurality of gas-flowing concave grooves on the side surface of the fuel cell that is in contact with the electrode. With a convex partition wall interposed between the concave grooves, in the solid polymer electrolyte fuel cell, the separator has a concave groove of any one separator, and a convex of the other separator. The partition walls are arranged so as to face each other with the fuel cell interposed therebetween, and 2) In the means described in the above item 1, the separator has a width dimension of the convex partition wall. The width is smaller than the width of the concave groove.

[0022]

According to the present invention, in the solid polymer electrolyte fuel cell, the separator is such that the concave groove of the separator for supplying the fuel gas and the convex partition wall for supplying the oxidant gas are interposed through the fuel cell. By being configured to be arranged at positions opposed to each other, since the PE film is not pressed from both sides at the top of the convex partition walls of both separators,
The occurrence of creep caused by being pressed by the tops is eliminated. In addition, since the separator according to the item (1) is configured such that the width dimension of the convex partition wall is narrower than the width dimension of the concave groove, it is considered that there is a dimensional error when manufacturing the solid polymer electrolyte fuel cell. However, if the dimensional error is within the difference between the width of the concave groove and the width of the convex partition, then P
Since the E film is not pressed from both sides at the top of the convex partition wall of both separators, it is possible to reliably eliminate the occurrence of creep caused by being pressed at the both tops. It becomes possible.

[0023]

Embodiments of the present invention will be described in detail below with reference to the drawings. Embodiment 1; FIG. 1 is a side sectional view schematically showing an expanded state of a solid polymer electrolyte fuel cell unit cell according to an embodiment of the present invention corresponding to claim 1. The same parts as those of the unit cell of the conventional solid polymer electrolyte fuel cell shown in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 1, 1 is a solid polymer electrolyte fuel in which the separators 2A and 2B are used instead of the separators 6A and 6B in the unit cell 5 of the conventional solid polymer electrolyte fuel cell shown in FIG. It is a battery cell.

The separator 2A has the same structure as the separator 6A, and the top of the convex partition wall 62A is formed to be flush with the side surface 2Aa. Further, in the separator 2B, concave grooves (gas distribution grooves) 61B are formed at positions facing the plurality of convex partition walls 62A of the separator 2A via the fuel cell unit 7, respectively. A convex partition wall 62B is formed at an intermediate position between the gas flow grooves 61B. Separator 2B
Also in the above, the top portion of the convex partition wall 62B is formed so as to be flush with the side surface 2Ba. Therefore, the gas distribution groove 61A of the separator 2A is located at a position opposed to the convex partition wall 62B of the separator 2B via the fuel cell unit 7. It should be noted that the unit cell 1 uses the unit cell 1 instead of the unit cell 5 of the conventional example in the stack 8 of the solid polymer electrolyte fuel cell illustrated in FIG. Make up a stack.

Since the present invention has the above-mentioned configuration, PE
The membrane 7C is a convex partition wall 6 of both separators 2A and 2B.
At the tops of 2A and 62B, there is no pressing from both sides via the fuel electrode 7A and the oxidant electrode 7B. As a result, the pressure on both tops causes P
The occurrence of creep that has occurred in the E film 7C is eliminated.
As a result, the film thickness of the PE film 7C, which has been generated at the top of the convex partition wall of the separator, does not decrease, and the tensile strength of the PE film 7C does not decrease at that position.

Embodiment 2 FIG. 2 is a side sectional view schematically showing a solid polymer electrolyte fuel cell unit cell according to an embodiment of the present invention in a developed state. A solid polymer electrolyte fuel cell unit cell according to an embodiment of the present invention corresponding to claim 1 shown in FIG. 1, and
The same parts as those of the unit cell of the conventional solid polymer electrolyte fuel cell shown in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 2, 3 is a separator 4A, 4B instead of the separators 2A, 2B for the unit cell 1 of the solid polymer electrolyte fuel cell according to one embodiment of the present invention corresponding to claim 1 shown in FIG. Is a unit cell of a solid polymer electrolyte fuel cell.

The separator 4A is different from the separator 2A shown in FIG. 1 in that a concave groove (gas distribution groove) 61A and a convex partition wall 62A are used instead of the concave groove (gas distribution groove) 41A and convex. The partition wall 42A in the shape of a circle is used. The top of the convex partition wall 42A is formed so as to be flush with the side surface 4Aa. In addition, the separator 4B
Is different from the separator 2B shown in FIG. 1 in that a concave groove (gas distribution groove) 41B and a convex partition wall 42B are used instead of the concave groove (gas distribution groove) 61B and the convex partition wall 62B. I am trying to use it. The top of the convex partition wall 42B is formed to be flush with the side surface 4Ba.

Here, the gas flow grooves 41A and 41B and the convex partition walls 42A and 42B are the convex partition walls 42A and 4B.
The width dimension of 2B (indicated by B in FIG. 2) is the groove width dimension of the gas distribution grooves 41A and 41B (A in FIG. 2).
Indicated by. ) Is smaller than In addition,
The unit cell 3 is a stack of the solid polymer electrolyte fuel cell by using the unit cell 3 instead of the conventional unit cell 5 in the stack 8 of the solid polymer electrolyte fuel cell illustrated in FIG. Constitute.

Since the present invention has the above-described structure, the PE film 7C is formed on both separators 4 as in the case of the first embodiment.
At the top of the convex partition walls 42A, 42B possessed by A, 4B, there is no pressing from both sides via the fuel electrode 7A and the oxidizer electrode 7B, but at that time, the solid polymer electrolyte type Even if there is a dimensional error when the fuel cell is manufactured, the dimensional error is caused by the gas flow grooves 41A, 4A.
1B groove width dimension; A and convex partition walls 42A, 42B width dimension; B; difference value between AB; PE film 7C is a convex partition wall of both separators 42
Fuel electrode 7A and oxidizer electrode 7 at the top of A and 42B
Since it is no longer pressed from both sides via B, it is possible to reliably eliminate the occurrence of creep that has occurred due to the pressing at both tops.

[0030]

EFFECTS OF THE INVENTION According to the present invention, with the above-mentioned constitution, the PE film thickness does not decrease at the position of the top of the convex partition wall of the separator, and the tensile strength of the PE film at that portion does not occur. Does not occur. As a result, the solid polymer electrolyte fuel cell can be stably operated for a long period of time without causing damage to the PE membrane at that portion. FIG. 3 shows an example of continuous operation data of a single cell of the solid polymer electrolyte fuel cell using the separator according to the present invention. Unlike the case of the solid polymer electrolyte fuel cell using the separator of the conventional example shown in FIG. 6, it has been confirmed that stable operation is performed for a long period of time, and the effect of the present invention is recognized.

[Brief description of drawings]

FIG. 1 is a side sectional view schematically showing a unit cell of a solid polymer electrolyte fuel cell according to an embodiment of the present invention corresponding to claim 1 in a developed state.

FIG. 2 is a side sectional view schematically showing a unit cell of a solid polymer electrolyte fuel cell according to an embodiment of the present invention corresponding to claim 2 in a developed state.

FIG. 3 is a graph showing an example of continuous operation data of a single cell of a polymer electrolyte fuel cell using a separator according to the present invention.

FIG. 4 is a side sectional view schematically showing an unfolded unit cell of a solid polymer electrolyte fuel cell of a conventional example.

FIG. 5 is a schematic configuration diagram of a solid polymer electrolyte fuel cell stack.

FIG. 6 is a graph showing an example of operation data of a single cell of a solid polymer electrolyte fuel cell using a separator of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 unit cell 2A separator 2B separator 3 unit cell 4A separator 4B separator 61A concave groove (gas distribution groove) 61B concave groove (gas distribution groove) 62A convex partition wall 62B convex partition wall 7 fuel cell

Claims (2)

[Claims] 1. A fuel cell which receives supply of a fuel gas and an oxidant gas to generate direct current power, and fuel cells which are arranged on both sides of the fuel cell to supply the fuel gas or the oxidant gas to the fuel cell. A separator having a plurality of gas flow grooves for, the fuel cell, an electrolyte layer made of a solid polymer electrolyte membrane, and electrodes arranged in close contact with each of the two main surfaces of the electrolyte layer. Each of the separators has a plurality of concave grooves for gas flow on the side surface in contact with the electrodes of the fuel cell, and a convex groove interposed between the concave grooves adjacent to each other. In the solid polymer electrolyte fuel cell having a partition wall, the separator has a concave groove of one of the separators and a convex partition wall of the other separator with a fuel cell interposed therebetween. Are intended to be arranged in mutually opposite positions Te, solid polymer electrolyte fuel cell characterized by. 2. The solid polymer electrolyte fuel cell according to claim 1, wherein the separator has a convex partition wall whose width dimension is narrower than that of a concave groove. Polymer electrolyte fuel cell.