JP3147518B2 - Cell structure of 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 solid polymer electrolyte fuel cell stack using a solid polymer membrane as an electrolyte membrane, and more particularly to a cell structure for humidifying the solid polymer membrane.

[0002]

2. Description of the Related Art FIG. 4 is a cross-sectional view schematically showing a single cell structure of a solid polymer electrolyte fuel cell.
It is composed of a solid polymer membrane 2 having ionic conductivity, a fuel electrode (anode electrode) 3 and an oxidant electrode (cathode electrode) 4 supported in close contact with both surfaces thereof. The bipolar plate 5 sandwiching the unit cell 1 is formed of a gas-impermeable plate having conductivity, and is formed as a fuel gas in a fuel gas passage 6 formed as a concave groove on the surface in contact with the fuel electrode 3. By supplying hydrogen as an oxidant to the oxidant passage 7 formed as a concave groove on the surface in contact with the oxidant electrode 4, power is generated based on an electrochemical reaction between the pair of electrodes of the single cell 1. Is performed. Since the output voltage of the single cell 1 having such a configuration is as low as 1 V or less, a stack of a plurality of single cells 1 and bipolar plates 5 is formed to obtain a solid output of a desired output voltage. A polymer electrolyte fuel cell is obtained.

On the other hand, as the solid polymer membrane 1 having ionic conductivity, for example, a membrane using a perfluorocarbon sulfonic acid membrane (Dupont, USA, trade name: Nafion) as a proton exchange membrane is used as an electrolyte membrane. It is known, has a proton (hydrogen ion) exchange group in the molecule, and exhibits a specific resistance of 20 Ω-cm or less at room temperature by containing saturated water,
In addition to functioning as a proton conductive electrolyte, it also functions as a diaphragm that prevents mixing of a fuel gas and an oxidizing gas. That is, on the anode electrode (fuel electrode) side, an anodic reaction (H ₂ → 2H ⁺ ) that decomposes hydrogen molecules into hydrogen ions and electrons.
+ 2e ⁻ ) at the cathode electrode (oxidant electrode) side, an electrochemical reaction (2) that produces water from oxygen, hydrogen ions and electrons.
H ⁺ +1/2 O ₂ + 2e ⁻ → H ₂ O), respectively, and an electrochemical reaction of H ₂ +1/2 O ₂ → H ₂ O is carried out as a whole. The generated power is supplied to the load by the electrons moving through the external circuit toward the load.

As described above, in a solid polymer electrolyte fuel cell, since the membrane functions as a proton exchange membrane by saturating the electrolyte membrane with water, the power generation efficiency of the solid polymer electrolyte fuel cell is increased. In order to maintain a high level, the solid polymer membrane 2 is maintained in a saturated water-containing state,
Operating temperature of the solid polymer electrolyte fuel cell is 50-100
It is necessary to keep the specific resistance of the solid polymer membrane low by keeping it at about ° C. For this reason, the assembly operation of the stack is performed in a state where the solid polymer electrolyte membrane 2 of each single cell 1 has been saturated with water in advance. However, when power is generated by raising the operating temperature to the above temperature range, the solid polymer membrane 2 shown below
This causes a problem that the solid polymer membrane 2 cannot be maintained in a saturated water-containing state and the power generation efficiency of the solid polymer electrolyte fuel cell decreases. That is, while the water generated by the electrochemical reaction by the fuel gas and the oxidizing gas is taken out of the system, the proton 2H ⁺ generated by the anodic reaction is converted from the anodic to cathodic by the proton 2H ⁺ generated in the anodic reaction.
When moving toward the proton, several molecules of water are oriented to the protons and move together, and are taken out of the system together with the fuel gas and the oxidizing agent, whereby the drying of the solid polymer membrane proceeds.

In order to avoid such a situation, water is added to the reaction gas (fuel gas and oxidizing agent) supplied to the reaction gas passages 6 and 7 so that the water vapor concentration (water vapor partial pressure) in the reaction gas is increased. Is known so that the evaporation of water from the solid polymer film 2 is suppressed. As a method for humidifying the reaction gas, a tank containing hot water is prepared outside the fuel cell, and the reaction gas is bubbled and humidified in the hot water, and the humidified reaction gas is supplied to each of the solid polymer electrolyte fuel cells. An external humidification method for supplying a single cell is known. There is also known an internal humidification method in which a humidification unit is provided adjacent to a solid polymer electrolyte fuel cell, and the reaction gas humidified here is supplied to each unit cell.

FIG. 5 is a schematic diagram showing a conventional solid polymer electrolyte fuel cell of the internal humidification system, and FIG. 6 is a schematic diagram showing a humidification unit in the conventional internal humidification system. In the figure, a solid polymer electrolyte fuel cell 10 is provided with a humidifying portion 11 for a reaction gas adjacent to a side wall thereof, and a humidified fuel gas and an oxidant are respectively supplied to a fuel gas passage 6 and an oxidant passage 7 of each unit cell. Supply. As shown in FIG. 6, the humidifying unit 11 is formed of a solid polymer membrane (membrane filter) having no electronic conductivity as humidifying water permeable membranes 12A and 12B. Is formed so as to face the fuel gas humidifying chamber 16 or the oxidizing agent humidifying chamber 17, and water vapor is generated from the surface of the humidifying water permeable membrane 12 moistened by the water heated by the exhaust heat of the fuel cell. The fuel gas and the oxidant are supplied to the fuel gas passage 6 of each unit cell of the polymer electrolyte fuel cell 10.
And the oxidant passage 7.

[0007]

The above-mentioned external humidification system requires heat insulation and heating of the piping in order to prevent the reaction gas humidified in the tank from condensing in the piping between the fuel cell and Since a heat source for heating the tank is required, there is a problem that the thermal efficiency of the solid polymer electrolyte fuel cell is reduced, and there is a drawback that the device becomes large-scale.

On the other hand, in the internal humidification method described above, the humidification unit is disposed adjacent to the fuel cell stack, so that the waste heat of the fuel cell as a heat source for generating steam can be easily used, and the humidification unit and the fuel cell There is an advantage that the gas piping between them can be simplified. However, since it is an independent device using a polymer membrane having no ionic conductivity as a water permeable membrane separately from the fuel cell, the number of parts is large, and there is a problem that the assembling work becomes complicated. Also, if the humidifying section can be laminated between the layers of the single cell, the latent heat of evaporation of the humidifying makeup water can be used for cooling the fuel cell, and the humidifying section is expected to be able to serve also as a cooling plate. Since the water-permeable membrane does not have electronic conductivity, stacking between layers of a single cell loses the conductivity of the stack, and there is also a problem that the humidifying portion cannot be used also as a cooling plate of a fuel cell.

An object of the present invention is to provide a solid polymer electrolyte type fuel cell having a humidifying section which is easy to assemble, has good humidifying performance and can contribute to cooling of the fuel cell by being integrated with the fuel cell stack. To obtain the cell structure of

[0010]

According to the present invention, there is provided a solid polymer membrane having ionic conductivity and a fuel electrode and an oxidant electrode which are disposed in close contact with both surfaces thereof. Solid polymer electrolyte type in which a plurality of single cells are laminated via a gas impermeable plate having a fuel gas passage or an oxidant passage formed of a concave groove in a portion facing each of the fuel electrode and the oxidant electrode. In a fuel cell, a gas humidifying passage formed as a concave groove communicating with the fuel gas passage or the oxidizing agent passage in one gas impermeable plate sandwiching a peripheral portion of the solid polymer membrane, and the other gas impermeable plate And a water supply passage formed as an independent concave groove at a portion facing the gas humidification passage. The fuel gas or the oxidant humidified by the gas humidification passage is supplied to the fuel gas passage. Others and be configured to be supplied to the oxidant passage.

Further, the humidifying sections are arranged at positions symmetrical to each other with respect to the solid polymer membrane, one of which forms a humidifying section for fuel gas and the other forms a humidifying section for oxidizing agent. It shall be.

[0012]

[0013]

With the above configuration, a solid polymer electrolyte fuel cell having a unitary cell humidifying unit for a reaction gas integrated with little change in the laminated structure of the solid polymer electrolyte fuel cell is constructed. Therefore, a function of avoiding an increase in the number of parts and the number of assembly steps can be obtained. In addition, the humidifying section is provided for each single cell, so the humidifying performance of the solid polymer membrane is excellent, and the transfer of moisture from the periphery of the solid polymer membrane to the main body can be expected. can get. In addition, the humidifying parts integrated on both sides of the single cell,
Since the heat generated by power generation of the single cell is taken as latent heat of vaporization of steam, the humidifying portion also serves as a cooling plate having a high response speed, and a function of improving the temperature distribution of the polymer electrolyte fuel cell is obtained.

Further, if the gas supply passage and the water supply passage in the two extended portions of the solid polymer membrane are arranged so as to be symmetrical to each other with respect to the solid polymer membrane, the fuel can be added to one of the extended portions. The humidifying portion of the gas and the humidifying portion of the oxidizing agent on the other extension portion can be formed without affecting the structure of the solid polymer electrolyte fuel cell. Furthermore, the fuel gas or the oxidant humidified in the gas humidifying passage is configured to be supplied to the fuel gas passage or the oxidizing agent passage, so that the required area of the humidifying unit can be reduced to a necessary minimum and the humidifying unit can be humidified. The function of efficiently humidifying the solid polymer membrane can be obtained without condensing water before the reaction gas humidified in the section is supplied to the fuel gas passage or the oxidizing agent passage.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. FIG. 1 is a cross-sectional view schematically showing a cell structure of a solid polymer electrolyte fuel cell according to an embodiment of the present invention. FIG. 2 is a plan view of a bipolar plate in the embodiment as viewed from a fuel gas passage side. FIG. 3 is a plan view of the bipolar plate in the embodiment as viewed from the oxidizing agent passage side. The same components as those in the prior art are denoted by the same reference numerals, and duplicate description will be omitted. In the figure, a solid polymer membrane 22 having ionic conductivity constituting a single cell is extended by a predetermined length to both sides of a fuel electrode 3 and an oxidant electrode 4 opposed to each other via this, and this extended portion is Water permeable membrane 22
A, 22B, a fuel gas humidifying part 3
6, a humidifying portion 37 of an oxidizing agent is formed on the other extension.

The humidifying section 36 of the fuel gas is
A fuel gas humidifying passage 26 as a groove communicating with the fuel gas passage 6 is formed in one of the bipolar plates 25A sandwiching the extended portion 22B of the second member 22 as a moisture permeable membrane.
Fuel gas humidifying passage 2 of the other bipolar plate 25B
Water supply passage 2 consisting of an independent concave groove at the portion facing 6
By forming the fuel cell 4, a solid polymer electrolyte fuel cell including the fuel gas humidifier 36 integrated with each unit cell is formed. As the oxidizing agent humidifying portion 37, the extended portion 22A of the solid polymer film 22 is used as a moisture permeable film, and is formed as a concave groove communicating with the oxidizing agent passage 7 to one of the bipolar plates 25B sandwiching the extended portion. The oxidizing agent humidifying passage 27 is formed, and the water replenishing passage 23 formed of an independent concave groove is formed in a portion of the other bipolar plate 25A facing the oxidizing humidifying passage 27, so that it is integrated with each single cell. A solid polymer electrolyte fuel cell including the humidified portion 37 of the converted fuel gas is configured.

The fuel gas humidifying portion 36 and the oxidizing agent humidifying portion 37 in one single cell are provided with gas humidifying passages 26 and 27 and water replenishing passages 23 and 24 in two extended portions of the solid polymer membrane. Are arranged symmetrically to each other with respect to the solid polymer membrane, so that one fuel gas humidifying passage 26 communicating with the fuel gas passage 6 and one oxidizing humidifying passage 27 communicating with the oxidizing agent passage 7 are provided. The solid polymer film 22 can be formed by using an extended portion of the solid polymer film 22.

Further, as shown in FIG. 2 or FIG. 3, the water supply passages 23, 24 are provided with bipolar plates 25A, 25A.
Rib 28 formed by connecting to seal portion 28 on the outer peripheral side of B
B, the gas passages 6 and 7 are defined and the inlets 23A and 24A of the makeup water penetrating the seal portion 28, and the outlets 23B and 23B.
Supply / drainage of makeup water is performed via 24B. The humidifying passage 26 for the fuel gas or the humidifying passage 27 for the oxidizing agent is provided between the fuel gas passage 6 and the oxidizing agent passage 7 by the rib 2.
8A, the fuel gas or the oxidizing agent passing through the humidifying passage is formed so as to make a U-turn and flow into the fuel gas passage 6 or the oxidizing agent passage 7 to condense the moisture in the reaction gas humidified in the humidifying passage. It is possible to supply the fuel gas to the fuel gas passage or the oxidant passage without causing the humidifying portion to occupy the minimum area.

The single cell having the cell structure according to the embodiment is as follows.
The replenishing water in the humidifiers 36 and 37 is heated by receiving the power generation heat of the single cell directly from the single cell or from an extension of a cooling plate (not shown), and is heated and wet.
Water vapor is generated on the surface of 22B, and the water vapor humidifies the reaction gas in the humidification passages 26 and 27, and the humidified fuel gas or oxidant is supplied to the fuel gas passage 6 and the oxidant passage 7 communicating therewith. You.

In the solid polymer electrolyte fuel cell constructed as a single cell laminate having the above-structured cell structure, the shape of the groove formed in the bipolar plate in advance is defined by the gas humidification passage, The solid polymer electrolyte fuel cell is provided with a humidifying part for the reaction gas integrated in each single cell without changing the layered structure of the solid polymer electrolyte fuel cell. Since the fuel cell can be configured, an increase in the number of parts and the number of assembly steps can be avoided, thereby reducing the manufacturing cost.In addition, a humidifying section is provided for each single cell, so that the humidifying performance of the reaction gas is good and wet. A solid polymer electrolyte fuel with a cell structure with a high degree of anti-drying performance, since moisture is transferred directly from the extension to the main body of the solid polymer membrane to prevent drying. It is possible to obtain pond advantageous in economical.

Further, since the humidifying portions integrated on both sides of the single cell deprive the power generation heat of the single cell as latent heat of vaporization of water vapor, the humidifying portion also functions as a cooling plate having a high response speed.
The advantage that the temperature distribution of the solid polymer electrolyte fuel cell can be improved can be obtained.

[0022]

According to the present invention, as described above, the humidifying part is integrated with the fuel cell compared with the external humidifying solid polymer electrolyte fuel cell, so that the humidifying tank and the gas pipe are required. In addition to simplifying the configuration of the device, the heat generated by the fuel cell can be directly used as a heat source for generating steam, so that the thermal efficiency is high, and the humidifying unit is provided in each unit cell to provide a high humidifying cell structure. A solid polymer electrolyte fuel cell can be provided economically and advantageously.

Further, as compared with the conventional solid polymer electrolyte type fuel cell of the internal humidification system in which a humidifying section is provided in the fuel cell, a humidifying section integrated with the fuel cell body is provided for each single cell, and the Since the generated heat can be used directly as a heat source for generating steam, the response speed of the humidification amount to changes in the temperature of the single cell is high, and it is expected that water can be directly replenished from the extension of the solid polymer membrane to the main body. An effect of preventing drying of the polymer film can be obtained. In addition, since the number of components and the number of assembling steps can be reduced by being integrated, an economic effect of significantly reducing manufacturing costs can be obtained. further,
Since the replenishing water supplied to the humidifying section also functions as cooling water, the same cooling effect as when a cooling plate is provided in each unit cell is obtained, and the surface direction of the unit cell and the stacking direction of the solid polymer electrolyte fuel cell Can also be expected to have a ripple effect of improving the temperature distribution and improving the cell characteristics.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a cell structure of a solid polymer electrolyte fuel cell according to an embodiment of the present invention.

FIG. 2 is a plan view of the bipolar plate in the embodiment as viewed from a fuel gas passage side.

FIG. 3 is a plan view of the bipolar plate in the embodiment as viewed from the oxidizing agent passage side.

FIG. 4 is a cross-sectional view schematically illustrating a single cell structure of a solid polymer electrolyte fuel cell.

FIG. 5 is a schematic view showing a conventional solid polymer electrolyte fuel cell of the internal humidification type.

FIG. 6 is a schematic view showing a humidifying unit in a conventional internal humidifying method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single cell 2 Solid polymer membrane 3 Fuel electrode 4 Oxidant electrode 5 Bipolar plate 6 Fuel gas passage 7 Oxidant passage 8 Gas seal part (rib) 10 Solid polymer electrolyte fuel cell (stack) 11 Humidification Unit 12 Humidification water permeable membrane 13 Humidification water passage 16 Fuel gas humidification chamber 17 Oxidizer humidification chamber 22 Solid polymer membrane 22A Extension of solid polymer membrane (moisture permeable membrane) 22B Extension of solid polymer membrane (moisture permeable membrane) 23) Water supply passage 24 Water supply passage 25A Bipolar plate 25B Bipolar plate 26 Fuel gas humidification passage 27 Oxidant humidification passage 28 Seal 28A Rib (for gas U-turn) 28B Rib (water (For defining the supply passage) 36 Fuel gas humidifier 37 Oxidizer humidifier

Claims (2)

(57) [Claims] 1. A single cell comprising a solid polymer membrane having ionic conductivity and a fuel electrode and an oxidant electrode which are disposed in close contact with both surfaces of the solid polymer membrane is opposed to the fuel electrode and the oxidant electrode, respectively. In a solid polymer electrolyte fuel cell in which a plurality of layers are stacked via a gas impermeable plate having a fuel gas passage or an oxidant passage formed of a concave groove, one of the gas impermeable members sandwiching the periphery of the solid polymer membrane A gas humidification passage formed as a groove communicating with the fuel gas passage or the oxidizing agent passage in the permeable plate, and an independent groove formed in a portion of the other gas impermeable plate opposed to the gas humidification passage. A humidifying section comprising a water supply passage, wherein the fuel gas or the oxidant humidified in the gas humidification passage is supplied to the fuel gas passage or the oxidant passage. Type fuel cell. 2. The humidifying section is arranged at positions symmetrical to each other with respect to the solid polymer film, one of which forms a humidifying section for fuel gas and the other forms a humidifying section for oxidizing agent. The solid polymer electrolyte fuel cell according to claim 1, wherein: