WO2007105291A1

WO2007105291A1 - Fuel cell

Info

Publication number: WO2007105291A1
Application number: PCT/JP2006/304877
Authority: WO
Inventors: Masami Tsutsumi
Original assignee: Fujitsu Limited
Priority date: 2006-03-13
Filing date: 2006-03-13
Publication date: 2007-09-20

Abstract

It is intended to realize a structure of simple architecture capable of close contact of MEA during power generation. There is provided a fuel cell comprising power generation part (15) having electrolyte layer (23) and, arranged opposite to each other with the electrolyte layer interposed therebetween, anode electrode (21) and cathode electrode (23) and comprising close contact retaining means (12) for mechanically effecting close contact and retention of the laminated structure by an exothermic reaction during the power generation of the power generation part.

Description

Specification

Fuel cell

Technical field

TECHNICAL FIELD [0001] The present invention relates to a fuel cell, and more particularly to a configuration of a fuel cell with improved durability.

Background art

[0002] Recent portable information devices have been further reduced in size, weight, and functionality! In addition, along with the development of information equipment, the battery used as a power source has steadily progressed in the small, light and high capacity. The most common driving power source in current mobile phone devices is a lithium ion battery. Lithium-ion batteries have a high driving voltage and battery capacity at the beginning of practical use, and performance improvements have been made in line with advances in mobile phone devices. However, there are limits to improving the performance of lithium-ion batteries, and lithium-ion batteries are no longer able to meet the demands for driving power sources for mobile phone devices that are becoming more sophisticated in the future.

[0003] Under such circumstances, development of a new power generation device to replace the lithium ion battery is expected. An example of such a power generation device is a fuel cell.

[0004] A fuel cell supplies a fuel electrode (anode electrode) with fuel, generates electrons and protons (H +), and reacts the protons with oxygen supplied to an air electrode (force sword electrode). This is a device that generates electricity. Electrons generated at the anode move to the power sword through the external circuit (conductor), and power can be taken out. The anode electrode and the force sword electrode are placed facing each other with the electrolyte layer in between. The structure of this power generation unit is called MEA (Membrane Electrode Assembly).

[0005] The greatest feature of a fuel cell system is that it can generate power continuously for a long time by replenishing fuel and oxygen. By replenishing the fuel instead of charging in the secondary battery, it can be applied to the equipment power supply in the same way as the secondary battery. For this reason, fuel cells are being actively researched and developed as ultra-compact power generation units that can be applied to notebook PCs and mobile phones that can be used not only as large generators for distributed power sources and electric vehicles. .

[0006] However, in particular, in a small fuel cell, when repeated discharge with poor durability is performed, the capacity decreases and there is a problem! This is MEA (Membran e Electrode Assembly) repeatedly generates electricity, causing peeling, resulting in inability to generate electricity! / I think.

[0007] In order to make the MEA difficult to peel off without using a holding jig, a pair of electrode substrates having a plurality of through-holes are embedded in both sides of the electrolyte by hot pressing, and the electrode substrates are inserted into the through-holes of the electrode substrate. There has been proposed a method for strengthening the joining by causing a solid electrolyte to penetrate (see, for example, Patent Document 1). In order to increase the adhesion between the fuel electrode and the solid electrolyte, a configuration in which a cermet layer, which is a composite material of metal particles and solid electrolyte particles, is inserted between the fuel electrode and the solid electrolyte has been proposed ( For example, see Patent Document 2). Patent Document 1: Japanese Patent Laid-Open No. 9-71889

Patent Document 2: JP 2004-362849 A

Disclosure of the invention

Problems to be solved by the invention

[0008] The conventional method described above has a problem that the MEA multilayer structure is complicated and the manufacturing process of the fuel cell is increased.

[0009] Therefore, an object of the present invention is to realize a structure capable of closely contacting the MEA during power generation with a simple structure.

Means for solving the problem

[0010] In order to solve the above problems, a close contact holding means capable of closely holding the MEA power generation unit by an exothermic reaction during power generation is provided.

[0011] As a first specific example, as a close-contact holding means, a housing is arranged facing the MEA, and the housing is made of a material that can be deformed as the temperature rises. The housing material bends in the direction of pressing the MEA due to the exothermic reaction during power generation.

As a second specific example, the MEA is fixed to the housing using a shape memory alloy panel, and the position of the housing material is changed in the direction of pressing the MEA due to the temperature rise during power generation.

[0012] More specifically, the fuel cell comprises:

(a) an electrolysis layer, and a power generation unit in which an anode electrode and a force sword electrode facing each other across the electrolyte layer are disposed,

(b) The laminated structure is mechanically held tightly by an exothermic reaction during power generation of the power generation unit. Close contact holding means

Is provided.

[0013] Corresponding to the first specific example, the close-contact holding means is a housing disposed to face the power generation unit, and the housing is made of a material that deforms as the temperature rises, for example, bimetal. Is done. As a good configuration example, the housing may have irregularities on the surface.

[0014] Corresponding to the second specific example, the close-contact holding means presses and holds the power generation unit against the housing as the temperature rises, and the housing is arranged to face the power generation unit. And a shape memory alloy panel.

The invention's effect

[0015] With a simple configuration, peeling of the MEA electrolyte layer and the electrode can be prevented. As a result, the durability of the fuel cell is improved.

Brief Description of Drawings

FIG. 1 is a diagram showing the appearance of a fuel cell according to one embodiment of the present invention and its cross-sectional structure.

FIG. 2 is a cross-sectional view showing a first configuration example of a fuel cell according to an embodiment of the present invention.

FIG. 3 is a view showing a pressing state of the housing against the MEA when the housing surface is uneven.

4 is a schematic cross-sectional view showing the configuration of the MEA of the fuel cell of FIG.

FIG. 5 is a cross-sectional view showing a second configuration example of a fuel cell according to an embodiment of the present invention.

FIG. 6 is a graph showing improved durability of the fuel cell of the present invention.

Explanation of symbols

[0017] 10 Fuel cell

12, 32 housing

13 Fuel tank

14 Vaporizer

15 Power Generation Department (MEA)

17 opening 18 Shape memory alloy panel

21 Fuel electrode (anode electrode)

22 Air electrode (force sword electrode)

23 Electrolyte layer

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 (a) is a schematic view showing an example of an external configuration of a fuel cell 10 according to an embodiment of the present invention, and FIG. 1 (b) is a longitudinal sectional view thereof. In the example of FIG. 1, the fuel cell 10 is accommodated in a fuel cell casing 11 having openings 17 on the front surface and the back surface.

[0020] The fuel cell 10 includes a fuel tank 13 that stores liquid fuel, a power generation unit (MEA) 15, and a vaporization unit that vaporizes the liquid fuel and supplies the fuel to the MEAl 5 in a gas phase. 14 and a housing 12 holding MEA 15. The liquid fuel is, for example, a 30% to 100% aqueous methanol solution, and preferably a 90% or higher aqueous methanol solution. The vaporization section 14 is a vaporized film formed of a non-porous material having methanol permeability, such as a perfluorosulfonic acid material, a perfluorosulfonic acid material having a carboxyl group, a silicone material, or a polyimide material ( And a mask layer with an opening (not shown) for preventing and holding the vaporized film from being deformed. MEA 15 includes an electrolyte layer 23 and a pair of electrodes 21 and 22 sandwiching the electrolyte layer 23.

Of the MEA 15 electrodes, the fuel electrode (anode electrode) 21 located on the fuel tank 13 side oxidizes the fuel supplied in the vapor phase from the vaporization section 14 to extract protons and electrons. That is, the anode electrode is an electrode on the side where the fuel is oxidized. The generated protons are transported to the air electrode (force sword electrode) 22 located on the opposite side of the fuel tank 13 through the electrolyte layer 23 formed of an ionic conductor having no electronic conductivity. The force sword electrode 22 generates water (steam) from ions generated by reducing oxygen and electrons and protons generated at the anode electrode 21. That is, the force sword electrode 22 is an electrode on the side which reduces at least oxygen as an active substance. The fuel housing 11 has an opening 17 so that outside air can be introduced into the force sword electrode 22.

[0021] For convenience of illustration, there is a wide gap between the vaporizer 14 and the fuel electrode 21 of the MEA 15. In fact, they are in close contact with each other, or a fuel diffusion layer (not shown) other than air is inserted between them.

[0022] In Fig. 1 (b), the fuel cell housing 11 has the openings 17 on the front and the back because it employs a series configuration in which the MEAs 15 are arranged on both sides of the fuel tank 13, respectively. The When the MEA 15 is disposed only on one side of the fuel tank 13, the opening 17 may be provided on either the front side or the back side.

[0023] Leads (not shown) are connected to the anode electrode 21 and the force sword electrode 22 of each MEA 15, and supply electrons generated by the anode electrode 21 to an external circuit.

[0024] The housing 12 fixes the MEA 15 during power generation to prevent the MEA 15 from peeling off from repeated discharge. In the present embodiment, the housing 12 is made of a bimetal material. In addition to this, any material may be used as long as it can be deformed as the temperature rises.

[0025] As shown in Fig. 2 (a), the housing 12 is arranged to face each of the MEAs 15 located on both sides of the fuel tank 13. The corner portion of each housing 12 is pressed against the casing 11 or the other housing 12 by a bolt or the like (not shown).

[0026] When the MEA 15 discharges, the temperature of the MEA 15 and its vicinity increases due to an exothermic reaction. As shown in Fig. 2 (b), the bimetal material is brought into close contact with the MEA 15 by bending in the direction in which the MEA 15 is pressed due to a temperature rise with a large curvature coefficient due to a temperature change. That is, the electrolyte layer 23, the fuel electrode 21, and the air electrode 22 are pressed and brought into close contact with each other.

[0027] A nanometal is a plate-like member in which two or more metals or alloys having different thermal expansion coefficients are bonded together. For example, two types of metal plates with different coefficients of thermal expansion are made by adding manganese, chromium, copper, etc. to an alloy of iron and nickel, and bonded together by cold rolling. In the example of Fig. 2 (b), the housing 12 is set so that the metal (or alloy) with the higher thermal expansion coefficient is located on the side in contact with the MEA 15.

FIG. 3 is a view showing a pressing state of the housing 12 against the MEA 15 when the surface of the bimetallic housing 12 is provided with irregularities. The bimetal housing 12 may have a flat surface as shown in Fig. 2. However, by providing irregularities on the surface as shown in Fig. 3, the adhesion spot for MEA15 with respect to 15 is increased and the adhesion effect is further enhanced. Can do. FIG. 4 is a diagram illustrating a configuration example of the MEA 15. The MEA 15 has a fuel electrode (anode electrode) 21 on one side of the electrolyte layer 23 and an air electrode (force sword electrode) 22 on the other side. In the anode electrode 21, an anode catalyst layer 21a and an anode current collector 21b are laminated in this order from the electrolyte layer 23 side. The anode catalyst layer 21a is made of a porous conductive material such as carbon paper containing fine particles of an alloy made of a transition metal such as platinum (Pt) or platinum and ruthenium (Ru), carbon powder, and high molecules forming the electrolyte layer 23. The film is applied and filled. The anode current collector 21b also has a metal mesh force such as SUS and Ni, and efficiently takes out the electrons generated in the anode catalyst layer 21a.

[0030] The force sword electrode 22 is laminated in the order of the force sword catalyst layer 22a and the force sword current collector 22b from the electrolyte layer 23 side. Similar to the anode catalyst layer 21a, the force sword catalyst layer 22a is composed of alloy fine particles made of a transition metal such as platinum (Pt), carbon powder, and a polymer that forms the electrolyte layer 23, such as carbon paper. A porous conductive film is applied and filled. The force sword current collector 22b also has a metal mesh force such as SUS or Ni, and efficiently supplies electrons to the force sword catalyst layer 22a.

[0031] The electrolyte layer 23 is a polyperfluorosulfonic acid polymer (resin) membrane represented by a Nafion membrane manufactured by DuPont. The electrolyte layer 23 itself is easily bent by the power generation of the MEA 15. This deflection causes the MEA 15 to peel off, but as shown in Fig. 2, the housing 21 that holds the MEA 15 is made of bimetal to maintain the introduction of air into the air electrode 22 while generating power. MEA can be pressed and held inside.

[0032] When fuel is supplied to the fuel electrode 21 via the fuel tank 13 and the vaporization unit 14 and power generation is started by the MEA 15, the MEA 15 gradually starts to generate heat. This heat generation raises MEA15 from about 20 ° C to 65 ° C. On the other hand, when a bimetal that deforms from 20 ° C to 65 ° C is used, it begins to bend gradually according to the temperature change of MEA15, and it is the most bent at a temperature at which power generation becomes constant, that is, 65 ° C. Will do. That is, the pressing force is strongest at the temperature at which peeling is most likely (65 ° C.). Therefore, the MEA can be pressed and held during power generation.

FIG. 5 is a diagram showing a second configuration example for fixing the MEA 15 during power generation. In the example of Fig. 5, MEA15 is held against Nosing 32 using shape memory alloy panel 18. To do.

[0034] A shape memory alloy is a material that returns to its original shape when heated even if it is deformed by applying a force at a temperature below the transformation point after processing the material into a certain shape and applying an appropriate heat treatment. have. Therefore, even if the panel in the compressed state is processed into the original shape with a shape memory alloy and then deformed at room temperature to extend the entire length of the panel, the original compressed shape is restored due to the increase in environmental temperature. Return.

Therefore, as shown in FIG. 5A, the MEA 15 is held against the nosing 32 by the shape memory alloy panel 18 deformed at room temperature. The housing 32 in FIG. 5 does not need to be made of bimetal, and for example, an appropriate material such as SUS or ceramics is used.

[0036] When the temperature rises due to the discharge of the MEA 15 during power generation of the fuel cell, the shape memory alloy vane 18 returns to its original compressed shape, and a force is applied in the direction in which the gusset 12 is pressed against the MEA 15. . By this pressing force, the fuel electrode, the air electrode, and the electrolyte layer can be brought into close contact with each other, and peeling can be prevented.

[0037] In this configuration as well, as in the configuration of FIG. 2, the MEA 15 can be held in close contact with each other even when the discharge accompanying the power generation of the fuel cell is repeated. Can be improved.

FIG. 6 is a graph showing improvement in durability of the fuel cell of the present invention. The horizontal axis of the graph is the number of repetitions, and the vertical axis is the discharge capacity. A square mark indicates a discharge capacity when the bimetallic housing 12 of the embodiment shown in FIG. 2 is used, and a diamond mark indicates a discharge capacity when a general SUS304 housing is used.

[0039] In the experiment, 2.5 cc of 100 vol% methanol was supplied, and the whole was discharged and counted as one time. At that time, the integrated value of the current flowing under the voltage of 2. OV was measured. Bimetal No. 5000 (manufactured by Fuji Metal Co., Ltd.) was used as the bimetal material for the housing 12. As catalyst layer 21a of fuel electrode (anode electrode) 21 of MEA15, platinum ruthenium (Pt—Ru) alloy supported catalyst (TEC61E54, made by Tanaka Kikinzoku) is used, and as catalyst layer 22a of air electrode (force sword electrode) 22, A platinum (Pt) supported catalyst (TEC10E70TPM, manufactured by Tanaka Kikinzoku) was used. As the electrolyte layer 23, Nafion NF112 manufactured by Dupont was used.

[0040] When a SUS304 housing is used, if the number of repeated discharges exceeds 10, The electric capacity is drastically reduced, and it hardly functions as a fuel cell. This is presumably because the impedance rapidly increases due to separation between the electrolyte layer and the electrode layer.

On the other hand, the fuel cell using the bimetal housing 12 as in the present embodiment has a substantially constant discharge capacity even after repeated discharges 50 times, and exhibits good durability. As described above, the bimetal housing 12 bends and presses in the direction in which the air electrode 22 is brought into close contact with the electrolyte layer 23 as the temperature rises with the power generation of the fuel cell, so that the MEA 15 is prevented from being peeled off. As a result, as shown in the graph, the durability of the fuel cell can be dramatically improved. As shown in FIG. 5, the same effect can be obtained when the shape memory alloy panel is used.

As described above, the present invention has been described based on the preferred embodiments. The present invention is not limited to these examples, and various modifications are possible. For example, in the configuration example of FIG. 2, an opening may be formed in the force housing 12 in which the housing 12 is installed independently of the fuel cell casing 11 and used as a part of the casing. Further, when the housing is used independently of the fuel cell casing 11 having the opening 17, the opening may be formed in the housing 12 itself.

Claims

The scope of the claims

[1] An electrolysis layer, and a power generation unit in which an anode electrode and a force sword electrode facing each other across the electrolyte layer are disposed,

An adhesion holding means for mechanically holding the laminated structure in close contact by an exothermic reaction during power generation of the power generation unit;

A fuel cell comprising:

2. The close contact holding means is a housing disposed to face the power generation unit, and the sawing and the swing are made of a material that deforms as the temperature rises. Fuel cell.

[3] The fuel cell according to [2], wherein the housing is made of metal.

4. The fuel cell according to claim 2, wherein the housing has irregularities on the surface.

[5] The close-contact holding means includes a housing disposed to face the power generation unit, and a shape memory alloy panel that presses and holds the power generation unit against the housing as the temperature rises. The fuel cell according to claim 1, wherein:

6. The fuel cell according to claim 2, wherein the housing has a plurality of openings.

[7] a fuel supply unit for supplying fuel to the power generation unit;

A vaporization unit that vaporizes the fuel supplied from the fuel supply unit;

The fuel cell according to claim 1, further comprising: a fuel in a gas phase supplied to the power generation unit.

8. The fuel cell according to claim 1, wherein the power generation unit includes a pair of power generation bodies arranged in series with the fuel supply unit interposed therebetween.