JP2002093434A - Electrolyte layer/electrode joint body and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the power density by surely reducing regions not contributing to the power generation of an electrolyte layer/electrode joint body by a simple constitution. SOLUTION: This electrolyte layer/electrode joint body is provided with a frame-shaped seal member 20 having its internal circumferential part stacked between the electrolyte layer 14 and an anode side electrode 16, and the frame- shaped seal member 20 is provided with a recessed/projecting portion 28 provided in the internal circumferential part along the planar direction for changing the stacking width dimension of the external/internal circumferential parts along the planar direction. The recessed/projecting portion 28 secures the seal width necessary for the sealing mechanism by the stack width dimension S1 of the recessed face 30 and the width dimension necessary for the support mechanism by the stack width dimension S2 of the projecting face 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte layer / electrode assembly and a fuel cell comprising a frame-shaped seal member superposed between an electrolyte layer and at least the anode electrode.

[0002]

2. Description of the Related Art A phosphoric acid type fuel cell (PAFC), which is one form of a fuel cell, is provided on both sides of an electrolyte layer in which phosphoric acid as a liquid electrolyte is impregnated in a polymer membrane such as polybenzimidazole. A unit power generation cell (unit fuel cell) constituted by sandwiching an electrolyte layer / electrode assembly composed of a pair of an anode electrode and a cathode electrode mainly composed of carbon with a separator (bipolar plate). Usually, a predetermined number of the unit power generation cells are stacked and used as a fuel cell stack.

On the other hand, a solid polymer fuel cell (SPFC)
Employs, for example, an electrolyte layer composed of an ion exchange membrane (cation exchange membrane) in which water is impregnated with polyfluoroethylene sulfonic acid or the like, and an electrolyte layer / electrode assembly similarly constituted by the electrolyte layer A predetermined number of unit power generation cells each composed of a fuel cell and a separator are stacked and used as a fuel cell stack.

In this type of fuel cell, a fuel gas supplied to an anode side electrode, for example, a gas mainly containing hydrogen (hereinafter also referred to as a hydrogen-containing gas) is formed by ionizing hydrogen on a catalyst electrode, and To the cathode side via the. The electrons generated during that time are taken out to an external circuit and used as DC electric energy. Since an oxidant gas, for example, a gas mainly containing oxygen or air (hereinafter also referred to as an oxygen-containing gas) is supplied to the cathode side electrode, hydrogen ions, electrons, And oxygen react to produce water.

In the above-described fuel cell, various sealing structures are employed in order to prevent contact between fuel gas and oxidizing gas, leakage of electrolyte, and the like. For example, US Pat. No. 700 (hereinafter referred to as "prior art 1") and Japanese Patent Application Laid-Open No. 62-4017.
A technique disclosed in Japanese Patent Publication No. 0 (hereinafter, referred to as Conventional Technique 2) is known.

In the above prior art 1, a sealing material, which is not a membrane electrode itself, is disposed in a frame shape around both sides of an ion exchange membrane. A frame-shaped sealing member (electrically insulating sheet seal) is interposed between the cell and one of the electrodes of the unit cell and the matrix in the inner peripheral area of the unit cell via packing. .

In the prior art 1, specifically, as shown in FIG. 8, an anode electrode 2 and a cathode electrode 3 are joined to both sides of the ion exchange membrane 1, and the outer peripheral edge of the ion exchange membrane 1 is formed. The joined portion is sandwiched between the inner peripheral portions of the frame-shaped gaskets 4a and 4b, which are sealing materials, to form the joined body 5.

[0008]

The gaskets 4a and 4b have a supporting function for holding the joined body 5 at a fixed position in the unit power generation cell.
The superposed portions (overlap portions) 6a and 6b provided on the inner peripheral portions of a and 4b need to have a bonding function for bonding the ion exchange membrane 1 in addition to the sealing function. Therefore, the width dimensions H1, H of the superposed portions 6a, 6b
2 is actually set to a size considerably larger than the width required for the sealing function.

However, the overlapping portions 6a, 6b
Has a structure in which the inner peripheral portions of the gaskets 4a and 4b are interposed between the ion exchange membrane 1 and the anode-side electrode 2 and the cathode-side electrode 3, and is a region that does not contribute to the power generation of the unit power generation cell. . Thereby, the overlapping portions 6a, 6b
It has been pointed out that as the width dimensions H1 and H2 become larger, the output density decreases, and stable power generation performance cannot be exhibited.

The present invention solves this kind of problem and provides an electrolyte layer / electrode assembly capable of securely holding the electrolyte layer by a frame-shaped seal member and improving the output density. The purpose is to:

Another object of the present invention is to provide a fuel cell which has a simple structure, can effectively maintain gas sealing properties, can effectively increase output per unit volume, and can be reduced in size. I do.

[0012]

In the electrolyte layer / electrode assembly according to the first aspect of the present invention, the inner peripheral portion of the frame-shaped seal member is overlapped between the electrolyte layer and at least the anode electrode. An uneven portion is provided on the inner peripheral portion along the surface direction. For this reason, in the inner peripheral portion of the frame-shaped seal member, the overlap width dimension is partially or continuously changed along the surface direction.

That is, while it is desired that the overlap width required for the sealing function is constant over the entire circumference, the supporting function of the electrolyte layer / electrode assembly is as follows.
What is necessary is just to join partially so that a positional change may not be caused. Therefore, a convex portion for achieving the support function and a concave portion for achieving the seal function can be partially or continuously provided on the inner peripheral portion of the frame-shaped seal member. As a result, power is generated in a portion corresponding to the concave portion.

As described above, the inner peripheral portion of the frame-shaped seal member has a fixed width portion having a seal width necessary for preventing a cross leak of the fuel gas or the oxidizing gas, the electrolyte layer and the frame-shaped seal. A part that protrudes inward from the constant width part is provided as a joint part for firmly joining the members, and a region contributing to power generation can be effectively expanded to improve power generation output. .

Further, in the fuel cell according to claim 2 of the present invention, the electrolyte layer / electrode assembly configured as described above is sandwiched by the separator having the gas flow path. For this reason, the output density of the fuel cell can be effectively improved, and when the fuel cells are stacked to form a fuel cell stack, the output per unit volume is improved and the fuel cell stack is improved. The overall size can be easily reduced.

[0016]

FIG. 1 is an exploded view showing the structure of an electrolyte layer / electrode assembly 10 according to a first embodiment of the present invention, and FIG. FIG. 3 is a sectional view taken along line III-III in FIG. 2, and FIG. 4 is an exploded view showing a configuration of a unit power generation cell 12 in which the electrolyte layer / electrode assembly 10 is incorporated.

The electrolyte layer / electrode assembly 10 includes an electrolyte layer 14 in which phosphoric acid is held in a porous material or a basic polymer formed of an inorganic material such as SiC, in particular, a polybenzimidazole matrix; 14, an anode 16 and a cathode 18 opposed to each other.
And a frame-shaped seal member 20 whose inner peripheral portion is overlapped between the electrolyte layer 14 and, for example, the anode 16.

The anode 16 and the cathode 18 are composed of an electrode catalyst layer 24 containing a catalyst for accelerating a reaction required for power generation at each electrode, and the electrode catalyst layer 24.
And a gas diffusion layer 26 that supplies a fuel gas and an oxidizing gas, which are reaction gases, to the electrode catalyst layer 24. The anode-side electrode 16 and the cathode-side electrode 18 are set to have the same dimensions as the electrolyte layer 14.

The frame-shaped seal member 20 is made of, for example, a polyimide film having a thickness of 25 μm. FIG.
As shown in FIG. 2, an uneven portion 28 is provided on the inner peripheral portion of the frame-shaped seal member 20 along the surface direction. The uneven portion 28 includes a concave surface 30 and the concave surface 3.
0, a convex surface 32 protruding inward from a predetermined position.
, And overlapping width dimensions S1 and S2 are set along the surface direction.

The overlap width S1 is set to a size suitable for a sealing function for preventing a cross leak between the fuel gas and the oxidizing gas, and the overlap width S2 is determined by the position of the electrolyte layer / electrode assembly 10. The dimensions are set to be suitable for the support function for joining without fluctuation. As shown in FIG. 2, a joining region 34 between the anode 16 and the electrolyte layer 14 is formed on the inner periphery of the frame-shaped seal member 20.

A fuel gas inlet 36a for allowing a fuel gas such as a hydrogen-containing gas to pass therethrough is formed on the outer peripheral side of the frame-shaped seal member 20 as a communication hole at an upper end on both ends in the longitudinal direction, and an oxidizing gas which is an oxygen-containing gas or air. An oxidizing gas inlet 38a for passing the oxidizing gas is provided. At the center of both ends in the longitudinal direction of the frame-shaped seal member 20, a cooling medium inlet 40a for passing a cooling medium such as pure water, ethylene glycol or oil as a communication hole, and a passage for passing the used cooling medium are used. A cooling medium outlet 40b is provided.

A fuel gas outlet 36b for passing a fuel gas and an oxidizing gas outlet 38b for passing an oxidizing gas are provided on the lower side of both ends in the longitudinal direction of the frame-shaped seal member 20. 36a and oxidant gas inlet 3
8a.

As shown in FIGS. 4 and 5, the unit power generation cell 12 is a phosphoric acid fuel cell (PAFC) whose operating (operating) temperature is set at around 120 ° C. to 200 ° C. A first separator and a second separator as a bipolar plate sandwiching the electrolyte layer / electrode assembly; the first and second separators and a frame-shaped sealing member; In between,
A seal member (gasket) 46 is provided.

The first and second separators 42 and 44 and the sealing member 46 are formed in substantially the same shape as the frame-shaped sealing member 20. The fuel gas inlet 36a and the oxidizing agent A gas inlet 38a is provided, a cooling medium inlet 40a and a cooling medium outlet 40b are provided at the center of both ends in the longitudinal direction, and a fuel gas outlet 36b and an oxidizing gas outlet 38b are provided at the lower parts at both ends in the longitudinal direction. Have been.

The anode 16 of the first separator 42
A plurality of, for example, four, independent first fuel gas passage grooves 48 are provided in the surface 42a facing to the fuel gas inlet 36a in the meandering direction in the horizontal direction in the direction of gravity. Can be The first fuel gas passage groove 48 joins the two second fuel gas passage grooves 50, and the second fuel gas passage groove 50 communicates with the fuel gas outlet 36b.

The cathode 18 of the second separator 44
Similarly to the first separator 42, a plurality of, for example, four independent first oxidizing gas flow grooves 52 are provided on the surface 44a facing the oxidizing gas inlet 38a.
Are provided in the direction of gravity while meandering in the horizontal direction. The first oxidizing gas passage groove 52 joins the two second oxidizing gas passage grooves 54, and the second oxidizing gas passage groove 54 communicates with the oxidizing gas outlet 38b.

The unit power generation cell 12 thus configured
Are stacked in a predetermined number in the direction of arrow A to form a phosphoric acid type fuel cell stack 56 as shown in FIG. At both ends in the stacking direction of the unit power generation cells 12, the unit power generation cells 1
Current collecting electrode 58 electrically connected integrally to
a, 58b are disposed, and the current collecting electrode 58
A predetermined number of cooling cells 60 are interposed between a and 58b. End plates 62a, 62 are provided outside the current collecting electrodes 58a, 58b via a sheet-shaped insulating member (not shown).
b, and the end plates 62a, 62b are fastened by tie rods or the like (not shown), whereby the unit power generation cell 12, the current collecting electrodes 58a, 58b, and the cooling cell 60 are integrally fastened and held in the direction of arrow A. You. For example, a load such as a motor (not shown) is connected to the current collecting electrodes 58a and 58b.

Next, the operation of manufacturing the electrolyte layer / electrode assembly 10 will be described.

First, after the inner peripheral portion of the frame-shaped seal member 20 is superimposed on the outer peripheral portion of the electrolyte layer 14,
4 on both sides of the anode electrode 16 and the cathode electrode 1
8 are arranged. In this state, pressurization and heat treatment are performed using a pressing device (not shown) under the conditions of a pressure of 4 × 10 ⁶ Pa, a temperature of 145 ° C., and a time of 30 seconds. As a result, the anode 16 and the cathode 18 are integrally joined to both surfaces of the electrolyte layer 14, and
The frame-shaped sealing member 20 is joined between the electrolyte layer 14 and the anode 16 to manufacture the electrolyte layer / electrode assembly 10.

Here, if the applied pressure is 4 × 10 ⁶ Pa or more, the anode electrode 16 itself and the cathode electrode 1
8 or the catalyst layer in the anode-side electrode 16 and the cathode-side electrode 18 may be damaged. On the other hand, if the applied pressure is 1 × 10 ⁶ Pa or less, the bonding strength may be insufficient. Therefore, the pressing force is 1 × 10 ⁶ Pa-
It is preferable that the pressure be in the range of 4 × 10 ⁶ Pa.

The temperature at the time of joining may be in the range of room temperature to 200 ° C., and if it exceeds 200 ° C., the electrolyte layer 1
There is a possibility that the phosphoric acid in 4 is concentrated and the film strength is reduced. The integration of the electrolyte layer 14 with the anode-side electrode 16 and the cathode-side electrode 18 is performed by an anchor effect at the interface between the polybenzimidazole film of the electrolyte layer 14 and the catalyst layer. For this reason, the temperature is preferably set in the range of 80 ° C. to 160 ° C., since it is necessary to soften the polybenzimidazole film to exhibit the anchor effect.

Further, even if the bonding time is set to be long, the bonding state is not improved, and it is necessary to set the time to be short from the viewpoint of productivity. Is concerned. For this reason, the joining time is preferably set within a range of 20 seconds to 60 seconds.

As the electrolyte layer 14, a material obtained by impregnating water with polytetrafluoroethylene sulfonic acid can be applied in addition to the above. At this time, the frame-shaped sealing member 2
The electrolyte layer / electrode assembly 10 is obtained by hot pressing or cold pressing using a thermoplastic elastomer sheet as 0.

The electrolyte layer / electrode assembly 10 manufactured as described above has a frame-shaped seal member 2 as shown in FIG.
A pair of seal members 46 are disposed so as to sandwich the outer peripheral side of the first and second separators 42 and 44 in contact with the seal member 46 and the anode 16 and the cathode 18. It is provided on both sides of the electrolyte layer / electrode assembly 10.

As a result, the unit power generation cells 12 are formed, a predetermined number of the unit power generation cells 12 are stacked in the direction of arrow A, and the cooling cells 60 are interposed. At both ends of the unit power generation cell 12 in the stacking direction, end plates 6
2a, 62b are disposed, and the end plate 62a,
The phosphoric acid type fuel cell stack 56 is assembled by integrally tightening and holding 62b via a tie rod (not shown).

The operation of the phosphoric acid type fuel cell stack 56 in which the unit power generation cells 12 configured as described above are incorporated will be described below.

In the phosphoric acid type fuel cell stack 56, a hydrogen-containing gas is supplied as a fuel gas to a fuel gas inlet 36a, air is supplied as an oxidant gas to an oxidant gas inlet 38a, and a cooling medium inlet 40a is A cooling medium is provided. The fuel gas is introduced into the first fuel gas passage groove 48 of the first separator 42 constituting each unit power generation cell 12, and the surface 42a of the first separator 42 meanders in the direction of arrow B in the direction of gravity. Moving. At this time, the hydrogen gas in the fuel gas is supplied to the anode 16. Then, the unused fuel gas is supplied to the second fuel gas passage groove 5.
It is discharged from 0 to the fuel gas outlet 36b.

On the other hand, the oxidizing gas is supplied to each unit power generation cell 12.
And moves in the direction of gravity while meandering in the horizontal direction (the direction of arrow B) on the surface 44a of the second separator 44 to form the second oxidation gas. The agent gas is supplied to the channel groove 54. in the meantime,
The oxygen gas in the oxidant gas is supplied to the cathode electrode 18, whereby power is generated by the electrolyte layer / electrode assembly 10.

As described above, the power generation in each unit power generation cell 12 causes the phosphoric acid type fuel cell stack 56
Current collecting electrodes 58a disposed on both ends in the stacking direction of
Electric power is supplied to a load (not shown) via 58b. The cooling medium supplied into the phosphoric acid type fuel cell stack 56 is supplied to the cooling cells 60 to cool the unit power generation cells 12, and then discharged from the phosphoric acid type fuel cell stack 56.

In this case, the electrolyte layer / electrode assembly 10 according to the first embodiment includes a frame-shaped seal member 20 between the electrolyte layer 14 and the anode 16 as shown in FIGS. The inner peripheral portion is overlapped, and an uneven portion 28 is provided on the inner peripheral portion along the surface direction. The concave-convex portion 28 has a concave surface 30 set to an overlap width dimension S1 corresponding to a seal width necessary for preventing a cross leak between the fuel gas and the oxidizing gas, and the electrolyte layer 14.
And a convex surface 32 having an overlapping width dimension S2 protruding inward from the concave surface 30 corresponding to a bonding width necessary for securely bonding the frame-shaped seal member 20.

As described above, the sealing width required for the sealing function is secured by the overlapping width dimension S1 of the concave surface 30, and the width dimension required for the supporting function of the entire electrolyte layer / electrode assembly 10 is set to the convex surface. 32 overlap width dimension S2
The frame-shaped sealing member 20
It is possible to effectively reduce the area of the bonding region 34 set at the inner peripheral portion of the first region. For this reason, the area of the electrolyte layer / electrode assembly 10 that does not contribute to power generation can be significantly reduced, and the effect that the output density can be effectively improved can be obtained.

Further, in the phosphoric acid type fuel cell stack 56 in which the electrolyte layer / electrode assembly 10 is incorporated, the output density per unit volume is improved, and the entire phosphoric acid type fuel cell stack 56 is easily miniaturized. There is an advantage that can be.

Further, in the first embodiment, the frame-shaped sheet member 20 is interposed between the anode 16 and the electrolyte layer 14. Here, at the anode 16, the fuel gas diffuses through the gas diffusion layer 26 to form the electrode catalyst layer 2.
When 4 is reached, 2H ₂ → 4H ⁺ + 4e ⁻ by the electrode catalyst.
As shown in (1), protons and electrons are generated. The protons move through the electrolyte layer 14 and move to the cathode 18
To the side.

On the other hand, the above-mentioned electrons reach the cathode side electrode 18 after being used as electric energy in the external load circuit. At the cathode 18, protons, electrons, and oxidant gas (oxygen gas) are acted upon under the action of an electrode catalyst.
, Power generation is continued through the reaction of O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O. In this power generation reaction, the reaction on the cathode 18 side is a rate-determining reaction.

At this time, as described above, the cathode 1
On the 8th side, the frame-shaped seal member 20 is not arranged,
The oxidizing gas diffuses through the gas diffusion layer 26 to form the electrode catalyst layer 24.
, The reaction field with protons is expanded, and the rate-limiting reaction can be promoted. Thereby, the power generation output of the electrolyte layer / electrode assembly 10 is effectively improved.

FIG. 7 is a front view of an electrolyte layer / electrode assembly 10a according to a second embodiment of the present invention. The first
The same components as those of the electrolyte layer / electrode assembly 10 according to the embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

The inner peripheral portion of the frame-shaped seal member 20a constituting the electrolyte layer / electrode assembly 10a is provided with a concave / convex portion 70 which deforms like a saw blade along the surface direction. The concave-convex portions 70 are provided with concave portions 72 and convex portions 74 alternately and continuously. The overlap width S1 of the concave portion 72 corresponds to a desired seal width, and the overlap width S2 of the convex portion 74 is set to a width satisfying a desired support function.

As a result, in the second embodiment, the area of the joining region 34 of the frame-shaped seal member 20a is greatly reduced, the region contributing to power generation is increased, and the output density can be easily improved. The same effects as those of the first embodiment can be obtained.

[0049]

In the electrolyte layer / electrode assembly according to the present invention, the inner peripheral portion of the frame-shaped seal member is provided with an uneven portion for changing the overlap width along the surface direction. The sealing function and the supporting function can be ensured, and the overlapping area can be effectively reduced. As a result, a region that does not contribute to power generation is reduced, and power generation output can be effectively improved.

Further, in the fuel cell according to the present invention, by using the above-mentioned frame-shaped sealing member, the output per unit volume is improved when the fuel cell stack is constructed, and the size of the entire fuel cell stack is reduced. Can be easily achieved.

[Brief description of the drawings]

FIG. 1 is an exploded view showing a configuration of an electrolyte layer / electrode assembly according to a first embodiment of the present invention.

FIG. 2 is a front view of the electrolyte layer / electrode assembly.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is an exploded view showing a configuration of a unit power generation cell into which the electrolyte layer / electrode assembly is incorporated.

FIG. 5 is a partially sectional explanatory view of the unit power generation cell.

FIG. 6 is a perspective view of a phosphoric acid type fuel cell stack in which the unit power generation cells are stacked.

FIG. 7 is a front view of an electrolyte layer / electrode assembly according to a second embodiment of the present invention.

FIG. 8 is a partial cross-sectional view of a unit power generation cell according to a conventional example.

[Explanation of symbols]

10, 10a ... electrolyte layer / electrode assembly 12 ... unit power generation cell 14 ... electrolyte layer 16 ... anode side electrode 18 ... cathode side electrode 20, 20a ...
Frame-shaped seal member 28, 70 ... Uneven portion 30 ... Concave surface 32 ... Convex surface 34 ... Joining area 36a ... Fuel gas inlet 36b ... Fuel gas outlet 38a ... Oxidizing gas inlet 38b ... Oxidizing gas outlet 40a ... Cooling medium inlet 40b cooling medium outlet 42, 44 separator 46 sealing member 48, 50 fuel gas flow channel 52, 54 oxidant gas flow channel 72 concave portion 74 convex portion

Claims (2)

[Claims] An electrolyte layer; an anode electrode and a cathode electrode provided on both sides of the electrolyte layer; and a frame shape in which an inner peripheral portion is overlapped between the electrolyte layer and at least the anode electrode. A seal member, wherein the inner peripheral portion of the frame-shaped seal member has the inner peripheral portion partially or continuously changed in a superposed width dimension along the planar direction. An electrolyte layer / electrode assembly characterized in that an uneven portion is provided along the surface. 2. A structure in which an anode-side electrode and a cathode-side electrode are provided on both surfaces of an electrolyte layer, and an inner peripheral portion of a frame-shaped seal member is overlapped between the electrolyte layer and at least the anode-side electrode. An electrolyte layer / electrode assembly to be provided, and a gas passage for sandwiching the electrolyte layer / electrode assembly, supplying a fuel gas to the anode electrode, and supplying an oxidizing gas to the cathode electrode. A separator, wherein the inner peripheral portion of the frame-shaped seal member is partially or continuously changed in a superimposed width dimension of the inner peripheral portion along the surface direction. A fuel cell, wherein uneven portions are provided along the fuel cell.