U.S. patent application number 10/706908 was filed with the patent office on 2004-05-20 for fuel cell, fuel cell generator, and equipment using the same.
Invention is credited to Imahashi, Jinichi, Kamo, Tomoichi, Oohara, Syuichi, Yamada, Norio, Yamaga, Kenji, Yoshikawa, Masanori.
Application Number | 20040096727 10/706908 |
Document ID | / |
Family ID | 18993884 |
Filed Date | 2004-05-20 |
United States Patent
Application |
20040096727 |
Kind Code |
A1 |
Kamo, Tomoichi ; et
al. |
May 20, 2004 |
Fuel cell, fuel cell generator, and equipment using the same
Abstract
To provide a compact power source best suited for portable use,
which uses no separator and has no auxiliary equipment such as a
fluid supply mechanism, and portable electronic equipment using the
power source. A fuel cell, a fuel cell generator, and electric
equipment using these have a construction such that the fuel cell,
having an anode for oxidizing liquid fuel, a cathode for reducing
oxygen, and an electrolyte membrane for insulating said the anode
from said the cathode, has a construction of a hollow support, the
anode, electrolyte membrane, and cathode are disposed on the outer
peripheral surface of the hollow support to form a generator
section, and the fuel is brought into contact with the inside of
the hollow support and gas containing the oxygen is brought into
contact with the outside of the generator section.
Inventors: |
Kamo, Tomoichi; (Tokai-mura,
JP) ; Oohara, Syuichi; (Hitachi, JP) ; Yamaga,
Kenji; (Hitachi, JP) ; Imahashi, Jinichi;
(Hitachi, JP) ; Yoshikawa, Masanori; (Hitachinaka,
JP) ; Yamada, Norio; (Hitachiohta, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-9889
US
|
Family ID: |
18993884 |
Appl. No.: |
10/706908 |
Filed: |
November 14, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10706908 |
Nov 14, 2003 |
|
|
|
09935164 |
Aug 23, 2001 |
|
|
|
Current U.S.
Class: |
429/454 ;
429/482; 429/506 |
Current CPC
Class: |
Y02E 60/50 20130101;
H01M 8/1009 20130101; H01M 8/2455 20130101; H01M 2300/0082
20130101 |
Class at
Publication: |
429/038 ;
429/030; 429/032 |
International
Class: |
H01M 008/24; H01M
008/10 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2001 |
JP |
2001-148602 |
Claims
What is claimed is:
1. A fuel cell, comprising: an anode for oxidizing liquid fuel; a
cathode for reducing oxygen; and an electrolyte membrane for
insulating said anode from said cathode, wherein said fuel cell has
a construction of a hollow support, and said anode, electrolyte
membrane, and cathode are disposed on the outer peripheral surface
of said hollow support to form a generator section, and said fuel
is brought into contact with the inside of said hollow support, and
gas containing said oxygen is brought into contact with the outside
of said generator section.
2. A fuel cell generator, wherein a fuel cell, having an anode for
oxidizing liquid fuel, a cathode for reducing oxygen, and an
electrolyte membrane for insulating said anode from said cathode,
has a construction of a hollow support; said fuel cell generator
includes a fuel cell unit in which a plurality of fuel cells each
having a generator section formed by said anode, electrolyte
membrane, and cathode disposed on the outer peripheral surface of
said hollow support are connected and a vessel for storing said
liquid fuel, said generator sections being connected electrically
to each other; and power is generated by supplying said liquid
fluid from said vessel into said hollow support.
3. The fuel cell generator according to claim 1, wherein a
diffusion layer is disposed around said cathode.
4. The fuel cell according to claim 1, wherein said hollow support
has electronic conductivity.
5. The fuel cell according to claim 1, wherein a holding material
for holding said liquid fuel is filled into said hollow
support.
6. The fuel cell according to claim 1, wherein a plurality of
generator sections comprising said anode, electrolyte membrane, and
cathode are disposed on the outer peripheral surface of said hollow
support, and said generator sections are electrically connected to
each other.
7. The fuel cell according to claim 2, wherein said vessel for
storing said liquid fuel has an exhaust hole of a gas-liquid
separation type.
8. A fuel cell generator, wherein said fuel cell generator has a
plurality of fuel cell units in-which a fuel cell has a
construction of a hollow support, and an anode for oxidizing liquid
fuel, a cathode for reducing oxygen, and an electrolyte membrane
for insulating said anode from said cathode are formed on the outer
peripheral surface of said hollow support in the order of said
anode, electrolyte membrane, and cathode, and a diffusion layer is
disposed around said cathode, whereby at least one generator
section is formed, said generator sections being connected
electrically to each other; and said fuel cell units are connected
to a fuel vessel for storing said fuel so that said fuel is
supplied from said fuel vessel to each of said fuel cell units,
said fuel cell units being connected electrically to each
other.
9. The fuel cell generator according to claim 8, wherein said fuel
is aqueous solution of methanol.
10. A portable power source, wherein said portable power source is
configured so as to include a fuel cell generator in which a fuel
cell has an anode for oxidizing methanol, a cathode for reducing
oxygen, and an electrolyte membrane for insulating said anode from
said cathode; said fuel cell has a construction of a hollow
support, and has a plurality of generator sections consisting of an
anode, electrolyte membrane, cathode, and diffusion layer on the
outer peripheral surface of said hollow support, said generator
sections being connected electrically to each other to form a fuel
cell unit; and a plurality of said fuel cell units are connected to
a vessel for storing liquid fuel, said fuel cell units being
connected electrically to each other.
11. Portable electronic equipment, wherein a fuel cell has an anode
for oxidizing methanol, a cathode for reducing oxygen, and an
electrolyte membrane for insulating said anode from said cathode;
said fuel cell has a construction of a hollow support, and has a
plurality of generator sections consisting of an anode, electrolyte
membrane, cathode, and diffusion layer on the outer peripheral
surface of said hollow support, said generator sections being
connected electrically to each other to form a fuel cell unit; a
plurality of said fuel cell units are connected to a vessel for
storing liquid fuel, said fuel cell units being connected
electrically to each other to form a fuel cell generator; and said
portable electronic equipment has at least a secondary battery that
is charged by a charger configured so as to include said fuel cell
generator.
12. Portable electronic equipment, wherein said portable electronic
equipment is driven by a fuel cell generator in which a fuel cell
has an anode for oxidizing methanol, a cathode for reducing oxygen,
and an electrolyte membrane for insulating said anode from said
cathode; said fuel cell has a construction of a hollow support, and
has a plurality of generator sections consisting of an anode,
electrolyte membrane, cathode, and diffusion layer on the outer
peripheral surface of said hollow support, said generator sections
being connected electrically to each other to form a fuel cell
unit; and a plurality of said fuel cell units are connected to a
vessel for storing liquid fuel, said fuel cell units being
connected electrically to each other.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a fuel cell that is formed
of an anode, electrolyte membrane, cathode, and diffusion layer and
is configured so that fuel is oxidized on the anode and oxygen is
reduced on the cathode. Also, it relates to a generator
incorporating such a fuel cell, a small-size portable power source,
and electric or electronic equipment using such a power source.
[0002] With advances in electronic technology, electric and
electronic equipment such as telephone sets, book type personal
computers, audio and visual equipment, and mobile information
terminals and small-sized portable electronic equipment have come
into wide use rapidly.
[0003] Conventionally, such portable electronic equipment has been
a system driven by a primary battery or a secondary battery. The
secondary battery has developed with emergence of new type
secondary batteries, decreased size and weight of battery, and the
high energy density technology. The new type secondary batteries
have developed from sealed lead batteries to nickel-cadmium
batteries, nickel-hydrogen batteries and further to lithium-ion
batteries. However, the secondary battery must be charged after a
fixed amount of electric power has been consumed, so that a
charging facility and charging time are needed. Therefore, there
remain many problems in driving the portable electronic equipment
continuously for a long period of time. In the future, the portable
electronic equipment will tend to necessitate a power source with a
high energy density, that is, a power source capable of
withstanding long-term continued use in response to increased
information amount and increased speed. Therefore, a need for a
small generator (micro-generator) that need not be charged is
increasing.
[0004] To fulfill this need, a fuel cell power source has been
proposed. The fuel cell converts chemical energy of fuel directly
into electrical energy in an electrochemical manner. It does not
necessitate a power section using an internal combustion engine
such as an ordinary engine generator, and has a possibility of
being used as a small power generating device. Also, the fuel cell
can continue power generation merely by replenishing fuel, so that
it can eliminate the need for stopping driving of portable
electronic equipment in use for the purpose of charging unlike the
conventional secondary battery.
[0005] Among these fuel cells, a polymer electrolyte fuel cell
(PEFC), in which by using an electrolyte membrane of
perfluorocarbon sulfonic acid, hydrogen gas is oxidized on the
anode and oxygen is reduced on the cathode to generate power, is
known as a cell with a high output density.
[0006] To make the fuel cell of this type smaller in size, as
disclosed in, for example, JP-A-9-223507 specification, a small
PEFC generator has been proposed in which an assembly of
cylindrical cells provided with anode and cathode electrodes on the
inside and outside surfaces of a hollow fiber shaped electrolyte is
formed, and hydrogen gas and air are supplied to the inside and
outside of the cylinder, respectively.
[0007] In the case were this fuel cell is used as a power source
for portable electronic equipment, however, the volumetric energy
density is low because the fuel is hydrogen gas, so that the
capacity of a fuel tank must be increased.
[0008] Also, this system requires auxiliary equipment such as
equipment for feeding fuel gas and oxidizer gas (air etc.) into the
generator and equipment for humidifying the electrolyte membrane to
maintain the cell performance, so that the generating system has a
complex construction, and cannot be made small in size
sufficiently.
[0009] In order to increase the volumetric energy density of fuel,
it is effective to use liquid fuel and to make the construction
simple by eliminating the auxiliary equipment for supplying fuel
and oxidizer to the cell. For this purpose, some proposals have
been made. As a recent example, a direct methanol fuel cell (DMFC),
in which methanol and water are used as fuel, as disclosed in
JP-A-2000-268835 specification and JP-A-2000-268836 specification
has been proposed.
[0010] This generator is configured so that a material for
supplying liquid fuel by the capillary force is provided on the
outside wall side of a liquid fuel tank, an anode is disposed so as
to be in contact with the material, and further a polymer
electrolyte membrane and a cathode are bonded successively. Oxygen
is supplied by the diffusion of oxygen to the cathode outside
surface touching the outside air. According to this system,
therefore, the generator has a simple configuration that does not
require the auxiliary equipment for supplying fuel and oxidizer
gas.
[0011] However, since the output voltage of DMFC at the load time
is 0.3 to 0.4 V per unit cell, it is necessary to mount fuel tanks
attached to the fuel cells, the number of the fuel cells
corresponding to the voltage required by portable electronic
equipment etc., and to connect the cells to each other in series.
Therefore, there arises a problem in that to make the size of
generator small, the capacity of fuel tank decreases with
increasing number of cells connected in series, so that the number
of fuel tanks is distributed according to the number of cells
connected in series.
SUMMARY OF THE INVENTION
[0012] An object of the present invention is to provide a fuel cell
generator capable of easily continuing power generation by the
replenishment of fuel without any need for charging each time a
fixed amount of electric power is consumed along with the use of
electric power unlike the secondary battery, which is a system
using a fuel with a high volumetric energy density.
[0013] Another objet of the present invention is to provide a
small-size power source suited for portable use, which has no need
for using auxiliary equipment such as a fluid supply mechanism for
forcedly causing fuel and oxidizer gas to flow, and portable
electronic equipment using the power source.
[0014] To attain the above objects, the present invention is
characterized by a fuel cell having an anode for oxidizing liquid
fuel, a cathode for reducing oxygen, and an electrolyte membrane
for insulating the anode from the cathode, wherein the fuel cell
has a construction of a hollow support, the anode, electrolyte
membrane, and cathode are disposed on the outer peripheral surface
of the hollow support to form a generator section, and the fuel is
brought into contact with the inside of the hollow support and gas
containing the oxygen is brought into contact with the outside of
the generator section.
[0015] Also, the present invention is characterized by a fuel cell
generator characterized in that a fuel cell, having an anode for
oxidizing liquid fuel, a cathode for reducing oxygen, and an
electrolyte membrane for insulating the anode from the cathode, has
a construction of a hollow support; the fuel cell generator
includes a fuel cell unit in which a plurality of fuel cells each
having a generator section formed by the anode, electrolyte
membrane, and cathode disposed on the outer peripheral surface of
the hollow support are connected and a vessel for storing the
liquid fuel, the generator sections being connected electrically to
each other; and power is generated by supplying the liquid fluid
from the vessel into the hollow support.
[0016] The small fuel cell generator in accordance with the present
invention is characterized in that in the fuel cell that uses
liquid fuel and is configured so that the anode for oxidizing fuel
and the cathode for reducing oxygen are disposed via the
electrolyte membrane, the fuel cell units each having a generator
section formed by the anode, electrolyte membrane, and cathode
disposed on the outer peripheral surface of the hollow support are
connected with the vessel for storing the liquid fuel being used as
a platform, the fuel cell units being connected electrically to
each other in series or in parallel.
[0017] Especially, in the case where the required current is
relatively small and a high voltage is needed, the fuel cell unit
is provided with a plurality of generator sections in which the
anode, electrolyte membrane, and cathode are disposed on the outer
peripheral surface of the hollow support, and the generator
sections are connected to each other in series with a conductive
interconnector, by which a high voltage can be achieved.
[0018] Fuel is supplied without any use of a forced supply
mechanism provided in the hollow support by connecting the fuel
tank as a platform. At this time, the hollow support is filled with
a material for holding liquid fuel and sucking it up by the
capillary force, by which fuel replenishment is more stabilized. On
the other hand, the fuel cell unit having the generator section on
the outer peripheral surface of the hollow support is supplied with
an oxidizer by the diffusion of oxygen in air. By using aqueous
solution of methanol with a high volumetric energy density as the
liquid fuel, power generation can be continued for a long period of
time as compared with the case where hydrogen gas in the tank
having the same capacity is used as a fuel.
[0019] By using the power source in accordance with the present
invention as a battery charger attached to charge a cellular phone,
portable personal computer, portable audio and visual equipment,
and other portable information terminals, which are mounted with a
secondary battery, during the time when they are not in use, or by
using the power source as a directly incorporated power source
without any secondary battery being mounted, the electronic
equipment can be used for a long period of time, and continuous use
of the electronic equipment can be achieved by the replenishment of
fuel.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIG. 1A is an outside construction view of a fuel cell unit
in accordance with the present invention, and FIG. 1B is a
sectional configuration view thereof;
[0021] FIG. 2A is an outside construction view of a fuel cell power
source in accordance with the present invention, and FIG. 2B is a
sectional configuration view thereof;
[0022] FIG. 3A is an outside construction view of a high-voltage
fuel cell unit in accordance with the present invention, and FIG.
3B is a sectional configuration view thereof;
[0023] FIG. 4 is a sectional configuration view of a fuel supply
port in accordance with the present invention;
[0024] FIG. 5A is an outside construction view of a square tubular
fuel cell unit in accordance with the present invention, and FIG.
5B is a sectional configuration view thereof;
[0025] FIG. 6 is a current/voltage characteristic diagram for a
fuel cell unit in accordance with a first embodiment and a second
embodiment;
[0026] FIG. 7A is an outside construction view of a cylindrical
fuel cell unit in accordance with the present invention, and FIG.
7B is a sectional configuration view thereof;
[0027] FIG. 8A is an outside construction view of a high-voltage
cylindrical fuel cell unit in accordance with the present
invention, and FIG. 8B is a sectional configuration view
thereof;
[0028] FIG. 9A is an outside construction view of a high-voltage
square tubular fuel cell unit in accordance with the present
invention, and FIG. 9B is a sectional configuration view
thereof;
[0029] FIGS. 10A and 10B are sectional configuration views of a
high-voltage square tubular fuel cell unit in accordance with the
present invention;
[0030] FIG. 11 is a current/voltage characteristic diagram for a
fuel cell unit in accordance with a third embodiment and a fourth
embodiment;
[0031] FIGS. 12A and 12B are views showing outside construction and
sectional construction of a separator in accordance with a
comparative example;
[0032] FIG. 13 is a view showing a laminating configuration of a
cell in accordance with a comparative example;
[0033] FIG. 14 is a construction view of a cell holder and a
tightening band for a cell in accordance with a comparative
example;
[0034] FIG. 15A is an outside construction view of a power source,
and FIG. 15B is a sectional view showing a state in which a fuel
tank is connected in accordance with a comparative example;
[0035] FIG. 16 is a construction view of a cell holder and a
tightening band for a cell in accordance with a comparative
example;
[0036] FIG. 17 is an outside construction view of a power source in
accordance with a comparative example;
[0037] FIG. 18A is an outside construction view of a power source
formed of square tubular fuel cell units, and FIG. 18B is a
sectional view showing a state in which a fuel tank is connected to
the fuel cell unit in accordance with the present invention;
[0038] FIG. 19 is a construction view of a cell holder for storing
square tubular fuel cell units in accordance with the present
invention;
[0039] FIG. 20A is an outside construction view of a power source
formed of cylindrical fuel cell units, and FIG. 20B is a sectional
view showing a state in which a fuel tank is connected to the fuel
cell unit in accordance with the present invention;
[0040] FIG. 21 is a construction view of a cell holder for storing
cylindrical fuel cell units in accordance with the present
invention;
[0041] FIG. 22A is an outside construction view of a power source
formed of high-voltage cylindrical fuel cell units, and FIG. 22B is
a sectional view showing a state in which a fuel tank is connected
to the fuel cell unit in accordance with the present invention;
[0042] FIG. 23A is an outside construction view of a power source
formed of high-voltage square tubular fuel cell units, and FIG. 23B
is a sectional view showing a state in which a fuel tank is
connected to the fuel cell unit in accordance with the present
invention;
[0043] FIG. 24A is an outside construction view of a cylindrical
fuel cell unit in accordance with the present invention, and FIG.
24B is a sectional configuration view thereof;
[0044] FIG. 25A is an outside construction view of a power source
formed of high-voltage cylindrical fuel cell units, and FIG. 25B is
a sectional view showing a state in which a fuel tank is connected
to the fuel cell unit in accordance with the present invention;
[0045] FIG. 26A is an outside construction view of a power source
formed of cylindrical fuel cell units, and FIG. 26B is a sectional
view showing a state in which a fuel tank is connected to the fuel
cell unit in accordance with the present invention; and
[0046] FIG. 27 is a sectional view showing a state in which an
auxiliary fuel tank is connected to a fuel tank for a power source
formed of cylindrical fuel cell units in accordance with the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0047] Embodiments of the present invention will now be described
in detail with reference to the accompanying drawings.
[0048] A construction of a fuel cell unit constituting one
embodiment of the present invention is schematically shown in FIG.
1A, and one sectional construction of a wall of the fuel cell unit
is shown in FIG. 1B.
[0049] An anode collector 6 is put around a hollow square tubular
support 1, and an anode electrode 3, an electrolyte 2, a cathode
electrode 4, a diffusion layer 5, and a cathode collector 7 are
laminated successively and bonded to form a generator section. This
is called a fuel cell, a fuel cell unit, or a unit cell. As
described later, a plurality of fuel cell units combined with each
other are called a fuel cell module or a modular cell.
[0050] At this time, a wall surface of the hollow support 1 covered
with the anode collector to which the anode is bonded has a wall
surface construction of a penetrating net shape or a penetrating
porous shape so that liquid fuel supplied in the tube comes into
contact with the anode. A construction of a power source in which a
fuel supply port 9 and a fuel discharge port 10 are connected to a
fuel tank 102 with a fuel cell module 101 constituted by a
plurality of fuel cell units being a platform is shown in FIG. 2A,
and a state in which the fuel tank is connected to the fuel cell
unit is shown in FIG. 2B.
[0051] The fuel tank 102 is provided with a fuel resupply port 103
on the top thereof, and aqueous solution of methanol is contained
therein as a fuel 104. By this configuration, fuel is supplied
without the use of a forced supply mechanism in the hollow support.
At this time, the fuel replenishment can be stabilized more by
filling a liquid holding material 14, which is a material for
holding liquid fuel in the hollow support and sucking it up by the
capillary force.
[0052] On the other hand, as shown in FIG. 1B, the cathode
electrode 4 has a construction such that oxygen in the atmosphere
is supplied by diffusion through the porous cathode collector 7 and
the diffusion layer 5, so that the cathode electrode 4 is supplied
with oxygen without the use of a forced supply mechanism for
oxidizer gas.
[0053] In the fuel cell using aqueous solution of methanol as a
fuel, electric power is generated by converting chemical energy of
methanol directly into electrical energy by the electrochemical
reaction shown below. On the anode electrode side, the supplied
aqueous solution of methanol reacts according to Formula (1) to be
dissociated into carbon dioxide, hydrogen ions, and electrons.
[0054] (1)
[0055] The yielded hydrogen ions move in the electrolyte membrane
from the anode to the cathode side, and react, on the cathode
electrode, with oxygen gas diffused from air and electrons on the
cathode electrode according to Formula (2) to yield water.
[0056] (2)
[0057] Therefore, the total chemical reaction causing power
generation is such that as shown in Formula (3), in which methanol
is oxidized by oxygen to yield carbon dioxide and water, and the
chemical formula is the same as that for flame combustion of
methanol.
[0058] (3)
[0059] The open-circuit voltage of unit cell is approximately 1.2
V, and is substantially 0.85 to 1.0 V due to the influence of fuel
permeating the electrolyte membrane. Although the practical voltage
in load operation is not subject to any special restriction, a
voltage region of about 0.3 to 0.6 is selected. Therefore, when the
fuel cells are used actually as a power source, the unit cells are
used by being connected in series so that a predetermined voltage
can be obtained according to the requirements of load equipment.
Although the output current density of unit cell is varied by the
electrode catalyst, electrode construction, and other factors,
design is made so that the power generation area of unit cell is
efficaciously selected so that a predetermined current can be
obtained. Also, the cell capacity can be regulated appropriately by
connecting unit cells in parallel.
[0060] The support constituting the fuel cell unit is characterized
by a tubular construction, which is one of the hollow support
constructions. The cross sectional shape of the support may be
square, circle, or others. It is not subject to any special
restriction as long as it can take a sufficient power generation
area in a compact manner.
[0061] However, in order to mount the fuel cell unit in a specified
volume in a compact manner, the cylindrical shape and the square
tubular shape have a high filling efficiency, and are preferable in
terms of workability for mounting the fuel cell generator
section.
[0062] The material for the support may be a material that is
electrochemically inert and has a sufficient strength with a thin
shape having durability in a service environment. There can be
cited, for example, polyethylene, polypropylene, polyethylene
terephthalate, vinyl chloride, polyacrylic resins and other
engineering resins, an electrical insulating material in which
these materials are reinforced by a filler etc., a carbon material
having high corrosion resistance in the yielded water generating
atmosphere, stainless steels, and an electroconductive material in
which the surface of ordinary iron, nickel, copper, aluminum, or an
alloy of these metals is subjected to corrosion resisting
treatment.
[0063] Also, it is effective to use an insulating material in which
a base metal having poor corrosion resistance is coated with the
aforementioned resin. Anyway, the material is not subject to any
special restriction as long as it has strength for supporting its
shape and corrosion resistance and is electrochemically inert.
[0064] The interior of the tubular support is used as a space for
conveying fuel. A sucking-up material that is filled in the tubular
support to stabilize the supply of fuel may be any material that
has a small contact angle with aqueous solution of methanol and is
electrochemically inert and corrosion resistant. As the sucking-up
material, powdery or fiber-like material may be used. For example,
glass, alumina, silica alumina, silica, non-graphite carbon, fiber
such as cellulose, and water absorbing polymeric fiber are
desirable materials because of low filling density and high
properties for holding aqueous solution of methanol.
[0065] A material in which fine particles of platinum and ruthenium
or platinum-ruthenium alloy are dispersedly carried on a carbon
powder carrier and a material in which fine particles of platinum
are dispersedly carried on a carbon carrier can be easily
manufactured and used as an anode catalyst forming the generator
section and a cathode catalyst, respectively.
[0066] The anode and cathode catalysts for the fuel dell in
accordance with the present invention are not subject to any
special restriction as long as they are the catalysts used for the
ordinary direct methanol fuel cell. As the electrolyte membrane, a
membrane exhibiting hydrogen ion conductivity is used. As the
membrane material, a sulfonated fluorine polymer represented by
polyperfluorostyrene sulfonic acid and perfluorocarbon sulfonic
acid, and a material in which a hydrocarbon polymer such as
polystyrene sulfonic acid, sulfonated polyether sulfones, and
sulfonated polyether ether ketons is sulfonated can be used. If
these materials are used as the electrolyte membrane, the fuel cell
can generally be operated at a temperature of 80.degree. C. or
lower.
[0067] Also, by the use of a composite electrolyte membrane in
which a hydrogen ion conductive inorganic material such as tungsten
oxide hydrate, zirconium oxide hydrate, and tin oxide hydrate is
dispersed microscopically in a heat-resistant resin, the fuel cell
can be operated in a higher temperature region. Anyway, if an
electrolyte membrane having high hydrogen ion conductivity and low
methanol permeability is used, the power generation utilization
factor of fuel increases, so that a smaller size of generator and
long-term power generation, which are the effects of the present
invention, can be achieved at a higher level.
[0068] The generator section forming the fuel cell unit can be
manufactured, for example, by the method described below.
Specifically, the fuel cell unit is manufactured in five steps: 1)
a step of applying a conductive collector around the hollow support
and making the wall surface of anode joint portion porous by means
of through holes, 2) a step of forming an electrode by applying a
paste-like substance to a porous portion of the hollow support to a
fixed thickness of 10 to 50 .mu.m, the paste-like substance being
obtained by adding and dispersing a solution in which the same
substance as the anode catalyst and the electrolyte membrane are
dissolved in advance in a volatile organic solvent as a binder, 3)
a step of applying an electrolyte solution dissolved in the
volatile organic solvent in advance onto the anode electrode so
that the thickness after membrane formation is 20 to 50 .mu.m, 4) a
step of forming the electrode by applying a paste-like substance
onto the electrolyte membrane to a fixed thickness of 10 to 50
.mu.m, the paste-like substance being obtained by kneading a
solution in which the same substance as the cathode catalyst and
the electrolyte membrane are dissolved in advance in a volatile
organic solvent as a binder, and 5). a step of forming the
diffuison layer by applying a paste-like substance onto the surface
of the cathode electrode, the paste-like substance being obtained
by mixing carbon powders with a predetermined amount of water
repellent dispersant, for example, aqueous dispersion of fine
particles of polytetrafluoroethylene.
[0069] At this time, it is important that in step 3), the
electrolyte membrane portion be made larger in area than the
cathode area, and the electrolyte membrane be brought into close
contact with the support or be bonded to the support using an
adhesive to provide a seal. The cathode portion of the obtained
fuel cell unit is mounted with a conductive porous material or net,
which is used as a cathode collector to take out a terminal, and a
terminal is also taken out from the anode collector.
[0070] When the fuel cell unit is formed of a single fuel cell,
step 1) is unnecessary, and an anode terminal can be taken out
directly by using the conductive hollow support. Also, when the
water repellent aqueous dispersion contains a surface active agent
serving as a catalytic poison component of platinum catalyst or
platinum-ruthenium alloy catalyst, a method is effective in which a
paste-like substance is applied onto one surface of a conductive
woven fabric such as carbon fiber, the paste-like substance being
obtained by mixing carbon powders with a predetermined amount of
water repellent dispersant, for example, aqueous dispersion of
polytetrafluoroethylene fine particles, and is fired at a
temperature at which the surface active agent decomposes, and then
the coated surface is mounted so as to be in contact with the
cathode to use the carbon fiber woven fabric as a cathode
terminal.
[0071] Besides, a method in which a membrane electrode assembly is
formed by applying the anode of a given thickness onto the inside
surface of the cylindrical electrolyte membrane and applying the
cathode and diffusion layer onto the outside surface thereof, and
the membrane electrode assembly is mounted on the tubular support,
and a method in which the anode, electrolyte membrane, cathode, and
water repellent layer are individually formed into a cylindrical
shape in advance, or some of these elements are combined and bonded
into a cylindrical shape, and these elements are mounted on the
support successively are also effective.
[0072] Furthermore, a method in which a membrane electrode assembly
obtained by applying the diffusion layer onto the outer peripheral
surface of cathode is mounted by winding the membrane electrode
assembly around the tubular support and bonding the joints of the
electrolyte membrane is also effective.
[0073] However, because the bonding of the anode, electrolyte
membrane, and cathode is a step of forming a reaction interface of
electrode, the bonding is desirably performed in advance by the
operation of applying the anode and cathode to the electrolyte.
[0074] Anyway, the manufacturing method for a fuel cell unit is not
subject to any special restriction as long as the method is such
that the anode, electrolyte membrane, cathode, and water repellent
layer are laminated on the surface of support in that order, and a
sufficient reaction interface is formed between the anode and the
electrolyte membrane and between the cathode and the electrolyte
membrane. Also, when the cathode is formed, a predetermined amount
of water repellent dispersant, for example, fine particles of
polytetrafluoroethylene is added to a solution in which the same
substance as the cathode catalyst and the electrolyte membrane are
dissolved in advance in a volatile organic solvent to form paste,
and the paste is applied, by which a cell without the need for the
water repellent layer can be manufactured.
[0075] Next, a construction for obtaining a higher voltage per fuel
cell unit will be described in detail with reference to FIG. 3A
showing the appearance of the fuel cell unit and FIG. 3B showing
one sectional construction of the wall thereof.
[0076] In this case, the hollow support 1 must be formed of an
electrical insulating material, and a plurality of net-like or
porous layers 8 are provided in a stripe form at the outer
periphery, the layer 8 forming a generator section of the hollow
support 1 to which the conductive anode collector 6 is applied. The
fuel discharge port 9 and supply port 10 are provided at the upper
and lower parts of the fuel cell unit, respectively. The unit cell
is formed by laminating the conductive porous anode collector 6,
the anode 3, the electrolyte membrane 2, the cathode 4, the
diffusion layer 5, and the net-like or porous cathode collector 7
in that order from the outside wall surface of the support 1, and
the cathode collector is connected to the adjacent anode collector
via an interconnector 11, by which cells are connected in series.
The unit cell is formed by the same method as described above. An
output terminal is taken out from the anode collector 6 at one end
and the cathode collector 7 on the other end.
[0077] The fuel tank is a structure that is also used as a platform
for a generator formed of one or more tubular fuel cells. The fuel
tank is formed of a material having structural strength and
corrosion resistance especially to aqueous solution of methanol.
There can be used polyethylene, polypropylene, polyethylene
terephthalate, vinyl chloride, polyacrylic resins and other
engineering resins, an electrical insulating material in which
these materials are reinforced by a filler etc., stainless steels,
and a material in which the surface of ordinary iron, nickel,
copper, aluminum, or an alloy of these metals is subjected to
corrosion resisting treatment.
[0078] Also, it is effective to use a material in which a base
metal having poor corrosion resistance is coated with the
aforementioned resin. The fuel tank is provided with mount ports
connected to the fuel supply and discharge ports of a plurality of
fuel cell units and one or more fuel resupply ports. The
constructions of the fuel supply and discharge ports are not
subject to any special restriction as long as the ports have an
airtight mechanism. In particular, if the fuel supply and discharge
ports are detachable, when a part of the fuel cell unit is
deteriorated, or other troubles occur, the entire fuel cell module
or a specific fuel cell unit is replaced, which provides a
preferable construction in which the power source can be used for a
long period of time.
[0079] During the power generation, the aqueous solution of
methanol in the fuel cell unit is oxidized, and thus carbon dioxide
is generated and returned to the fuel tank through the discharge
port of the fuel cell unit, which increases the pressure in the
tank. Also, by a change in environmental temperature, especially by
a shift from a low-temperature environment to a high-temperature
environment, the pressure in the fuel tank is increased. In order
to avoid such a phenomenon, it is effective to provide a mechanism
for selectively permeating gas at the fuel resupply port.
[0080] Also, as another embodiment, a construction can be adopted
in which in addition to the fuel tank serving as a platform for a
fuel cell unit group, an auxiliary fuel tank can be mounted on the
platform to prolong the duration of power generation. In this case,
it is preferable that the platform tank be provided with a receipt
port mechanism, and the auxiliary tank be provided with a mount
port mechanism and a fuel resupply port having a mechanism for
selectively permeating gas.
[0081] FIG. 4 shows a cross-sectional construction of a specific
embodiment of the mechanism for selectively permeating gas. A lid
51 for a fuel resupply port 53 is provided with a plate formed with
one or more pinholes whose inside surface is water repellent or a
porous water repellent plate 52. The lid 51 and the fuel resupply
port 53, and the fuel supply port and the fuel tank are fixed to
each other with a screw construction having airtightness. If the
gas temperature in the tank is increased by the generation of
carbon dioxide due to power generation or the rise in environmental
temperature, gas is selectively permeated or discharged through
many pinholes or porous plate, so that liquid fuel does not flow
out.
[0082] The fuel cell unit having a plurality of generator sections
each provided with the anode, electrolyte membrane, and cathode
around the hollow support, which are a characteristic of the
present invention, is manufactured, the generator sections are
connected in series by the conductive interconnector to achieve
high voltage, and the fuel tank is connected as the platform.
Thereby, a small power source can be realized in which fuel is
supplied into the hollow support without the use of a forced supply
mechanism, an oxidizer is supplied from the outside surface of each
fuel cell unit by the diffusion of oxygen in air, and power
generation can be continued for a long period of time by using
aqueous solution of methanol having a high volumetric energy
density as liquid fuel. This small power source can be driven by
being incorporated as a power source for, for example, a cellular
phone, a book type personal computer, and a portable video camera,
and the long-term continued use of the power source can be achieved
by successively replenishing the fuel having been prepared in
advance.
[0083] Also, in order to significantly decrease the frequency of
fuel replenishment as compared with the above-described case, it is
effective to use this small power source as a battery charger by
connecting the power source to a charger for, for example, a
cellular phone, a book type personal computer, and a portable video
camera, which are mounted with a secondary battery, and by mounting
it at a part of a storage case thereof. In this case, when the
portable electronic equipment is being used, the equipment is taken
out of the storage case and is driven by the secondary battery, and
when the equipment is not in use, the equipment is stored in the
storage case, and the small fuel cell generator incorporated in the
storage case is connected to the equipment via the charger to
charge the secondary battery. Thereby, the capacity of fuel tank
can be increased, and thus the frequency of fuel replenishment can
be decreased significantly.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0084] The present invention will now be described in more detail
with reference to embodiments. The gist of the present invention is
not limited to the embodiments described below.
[0085] The following will be a description of a first embodiment of
the present invention.
[0086] An outside construction of a tubular fuel cell unit in
accordance with the first embodiment of the present invention is
shown in FIG. 5A, and the sectional configuration thereof is shown
in FIG. 5B.
[0087] The hollow support 1 was made of a 0.4 mm thick stainless
steel SUS304 coated with hydroxyl group containing polyacrylic
resin clear paint (manufactured by Kansai Paint Co., Ltd.), and was
a square tubular vessel having outside dimensions of 4 mm.times.3
mm and a height of 44 mm. The hollow support 1 was filled with
glass fiber with a porosity of 85% as the liquid holding material
14.
[0088] The square tube was provided with airtightness by bonding
lids 12 and 13 of an acrylic board with a thickness of 2 mm to the
top and bottom of the tube, respectively.
[0089] On the outer peripheral surface of the square tube, there is
provided the porous layer 8 with a porosity of about 70%, which is
formed with through holes with a diameter of about 1 mm, and in the
upper and lower portions without holes on the side of square tube,
there are provided the fuel discharge port 9 and the supply port
10, which have an outside diameter of 3 mm and an inside diameter
of 2 mm.
[0090] The porous layer 8 of this square tube was covered with a
stainless steel SUS316 mesh serving as an anode collector 6, 5% by
weight of aqueous solution of Nafion 117 alcohol (mixed solvent of
water, isopropanol, and normal propanol in the weight ratio of
20:40:40, manufactured by Fluke Chemical Corp.), in which the
electrolyte amount corresponded to 60 wt % of catalyst amount by
dry weight, was added to a platinum-ruthenium carrying carbon
catalyst and was kneaded to form paste, and the paste was applied
onto the mesh so that the thickness after drying was performed at
60.degree. C. for three hours was 30 .mu.m, by which the anode 3
was formed.
[0091] After drying was performed at a temperature of about
60.degree. C. for three hours, the quantity of platinum was 2
mg/cm.sup.2, and the quantity of ruthenium was 1 mg/cm.sup.2.
[0092] Then, after the drying at 60.degree. C., 5% by weight of
aqueous solution of Nafion 117 alcohol was evaporated, and a liquid
concentrated to about 30% by weight was applied to the entire outer
peripheral surface of square tube so that the electrode section had
a thickness of about 50 .mu.m, by which the electrolyte membrane 2
was formed.
[0093] After drying was performed at room temperature for 10 hours
and subsequently drying was performed at 60.degree. C. for three
hours, the coat thickness in the non-electrode section was
measured. The measurement result was such that although the corner
portion of the square tube had a slightly greater thickness, the
flat portion thereof had a thickness in the range of 73 to 76
.mu.m, and the thickness of electrolyte membrane in the current
carrying portion was about 45 .mu.m.
[0094] Five percent by weight of aqueous solution of Nafion 117
alcohol, in which Nafion 117 corresponded to 60 wt % of catalyst
amount by dry weight, was added to a platinum carrying carbon
powder catalyst and was kneaded to form paste, and the paste was
applied onto the formed electrolyte membrane 2 in such a manner as
to overlap with the anode 3 so that the thickness after drying was
15 .mu.m, by which the cathode 4 was formed after drying at
60.degree. C. for three hours. The quantity of platinum at this
time was about 0.8 mg/cm.sup.2.
[0095] Next, aqueous dispersion of water repellant of fine
particles of polytetrafluoroethylene (Teflon Dispersion D-1,
manufactured by Daikin Industries, Ltd.) was added to carbon
powders so that the weight after firing was 40 wt %, and kneaded to
form paste. The paste was applied onto one surface of carbon fiber
nonwoven fabric having a thickness of about 100 .mu.m and a
porosity of 87% so that the thickness was about 20 .mu.m, and
drying was performed at room temperature and then firing was
performed at 270.degree. C. for three hours to form the diffusion
layer 5.
[0096] The obtained diffusion layer 5 was cut into a tape shape
having the same width as the cathode width of the square tubular
fuel cell, and the tape was wound on the cathode of the square
tubular fuel cell so that the joints did not lap on each other.
Thereby, a stainless steel SUS3316 mesh was fixed to the diffusion
layer 5 as the cathode collector 7. To the end portions of the
anode and cathode collectors 6 and 7, terminals of the fuel cell
unit were connected.
[0097] The square tubular fuel cell unit obtained in this manner
was a single cell having a fuel filling volume of about 0.26
cm.sup.3 and a power generation effective area of about 5 cm.sup.2.
The current/voltage characteristics of initial characteristics of
unit cell at 55.degree. C., which was measured by filling 10 wt %
of aqueous solution of methanol as a liquid fuel, exhibited an
output voltage of 0.30 V at a load current density of 150
mA/cm.sup.2 as indicated by curve 61 in FIG. 6. When a power source
is formed by mounting a plurality of fuel cell units having such a
construction, the fuel cell units can be arranged and mounted in a
compact manner merely by providing a space necessary and sufficient
for the diffusion of air.
[0098] The following will be a description of a second embodiment
of the present invention.
[0099] An outside construction of a fuel cell unit having a
cylindrical construction, which uses aqueous solution of methanol
as a fuel, in accordance with another embodiment of the present
invention is shown in FIG. 7A, and a sectional configuration
thereof is shown in FIG. 7B.
[0100] The hollow cylindrical support 1 was formed of a
polypropylene-made cylinder measuring 4.5 mm in outside diameter,
3.6 mm in inside diameter, and 44 mm in length, and a copper-made
anode terminal strip 15 with a width of 3 mm and a thickness of 0.2
mm fitted beforehand around one end of the cylinder. The anode
collector 6 was formed by applying a conductive carbon paint with a
thickness of about 50 .mu.m around the support 1 with
polyvinylidene fluoride being used as a binder. On a 38 mm wide
cylindrical wall surface to which the anode collector 6 is applied,
the porous layer 8 was provided in which through holes 8 with a
diameter of about 0.5 mm were formed so that the porosity was about
65%.
[0101] Glass fiber with a porosity of 85% was filled into the
cylinder as the liquid holding material 14, and the 2 mm thick
polypropylene-made lids 12 and 13 having the fuel discharge port 9
and the supply port 10 each having an outside diameter of 3 mm and
an inside diameter of 2 mm were welded to the top and bottom of the
cylinder, respectively, to provide airtightness. Next, 5% by weight
of aqueous solution of Nafion 117 alcohol, in which Nafion
corresponded to 60 wt % of catalyst amount by dry weight, was added
to a platinum-ruthenium carrying carbon catalyst and kneaded to
form paste, and the paste was applied onto the area of 38
mm.times.12 mm of the electrolyte membrane 2 of Nafion 117
(manufactured by Du Pont) measuring 44 mm.times.14 mm and 50 .mu.m
thick by the screen printing process to form the anode 3. After
drying at about 60.degree. C. for three hours, the quantity of
platinum was about 1.3 mg/cm.sup.2, and the quantity of ruthenium
was about 0.65 mg/cm.sup.2.
[0102] Next, 5% by weight of aqueous solution of Nafion 117
alcohol, in which Nafion corresponded to 60 wt % of catalyst amount
by dry weight, was added to a platinum carrying carbon powder
catalyst and kneaded to form paste, and the paste was applied on
the surface opposite to the surface onto which anode 3 had been
applied of the electrolyte membrane 2 by the screen printing
process in such a manner as to overlap with the anode 3 so that the
thickness after drying was 15 .mu.m, by which the cathode 4 was
formed after drying at 60.degree. C. for three hours. Thereby, the
membrane electrode assembly was formed.
[0103] At this time, the quantity of cathode platinum was about 0.8
mg/cm.sup.2. Next, aqueous dispersion of water repellant of fine
particles of polytetrafluoroethylene was added to carbon powders so
that the weight after firing was 40 wt %, and kneaded to form
paste. The paste was applied onto one surface of carbon fiber
nonwoven fabric having a thickness of about 100 .mu.m and a
porosity of 87% so that the thickness was about 20 .mu.m, and
drying was performed at room temperature and then firing was
performed at 270.degree. C. for three hours to form the diffusion
layer 5.
[0104] A silicone liquid gasket 16 was applied to potions with a
width of about 2.5 mm in which electrolyte membrane of the upper
and lower peripheries of the membrane electrode assembly was
exposed and was wound so as to cover the porous layer 8 of the
cylindrical hollow support 1, and the upper and lower ends were
bonded. A liquid formed by concentrating 5% by weight of aqueous
solution of Nafion 117 alcohol to about 30% by weight was applied
to the electrolyte membrane joint exposed in the lengthwise
direction of the cylindrical support 1 of the membrane electrode
assembly while the electrolyte membrane is tightened from the outer
periphery, and the joint was connected by drying at 60.degree. C.
for about three hours.
[0105] The obtained diffusion layer 5 was cut into a tape shape
having the same width as the cathode width, and the tape was wound
on the cathode of the cylindrical fuel cell so that the joints did
not lap on each other. A copper-made mesh was fixed to the porous
cathode collector 7 coated with a conductive carbon paint with
polyvinylidene fluoride being used as a binder so that the mesh was
used as the cathode terminal.
[0106] Also, seal portions at both ends of the cylindrical fuel
cell unit were tightened with a rubber-based tightening band 17 and
were fixed. The obtained cylindrical fuel cell unit was a single
cell having a fuel filling volume of about 0.37 cm.sup.3 and a
power generation effective area of about 4.5 cm.sup.2. The initial
current/voltage characteristics of unit cell at 55.degree. C.,
which was measured by filling 10 wt % of aqueous solution of
methanol as a liquid fuel, exhibited an output voltage of 0.32 V at
a load current density of 150 mA/cm.sup.2 as indicated by curve 62
in FIG. 6.
[0107] If the fuel cell unit is formed into a cylindrical shape as
in the case of this embodiment, a process for joining cell members
at the outer periphery of the hollow support can be made easy, the
tightening by the porous cathode collector 7 can be made uniform,
and the output voltage of unit cell can be made high.
[0108] The following will be a description of a third embodiment of
the present invention.
[0109] An outside construction of a high-voltage fuel cell unit
having a cylindrical construction, which uses aqueous solution of
methanol as a fuel, in accordance with still another embodiment of
the present invention is shown in FIG. 8A, and a sectional
configuration thereof is shown in FIG. 8B.
[0110] A polypropylene-made hollow cylinder measuring 6.4 mm in
outside diameter, 5.5 mm in inside diameter, and 90 mm in length,
which had two ribs 21 with a width of 1.5 mm and a height of 50
.mu.m at the outer periphery thereof at positions 30 mm from both
ends was manufactured, and the copper-made anode terminal strip 15
with a width of 3 mm and a thickness of 0.2 mm was fitted
beforehand around a portion where the 3 mm wide upper end portion
of the cylinder was cut to an outside diameter of 6.0 mm, by which
the hollow cylindrical support 1 was formed. The outer peripheral
surface excluding the anode collector 6 on the rib surface and at
the support end was masked by a resin tape, and a conductive carbon
paint with a thickness of 50 .mu.m was applied to the remaining
outer peripheral surface with polyvinylidene fluoride being used as
a binder, by which the anode collector 6 connected by the
interconnector 11 was formed. Three collector forming sections each
having a width of 25 mm were provided in contact with one side face
of the rib so that through holes with a diameter of about 0.5 mm
were formed with a porosity of about 65%, by which the porous
sections 8 were formed. Onto the surface of collector divided into
three, the anode 3 with a thickness of 30 .mu.m was applied by the
same method as that of the first embodiment. Then, the anode
collector of the rib 21 and the interconnector 11 was masked, and
the electrolyte membrane 2 was formed on the anode 3 formed in the
current carrying portion and in a portion of anode collector that
was not masked by the same method as that of the first embodiment
so that the current carrying portion had a thickness of about 40
.mu.m.
[0111] Next, the cathode 4 with a thickness of 15 .mu.m was formed
on the electrolyte membrane 2 at a position such as to overlap with
the anode 3 by the same method as that of the first embodiment. The
diffusion layer 5 formed by the same method as that of the first
embodiment and the cathode collector 7 that is the same as that
used in the second embodiment 2 were lapped on each other, and the
outer periphery was fixed by a polyethylene-made tightening mesh
20.
[0112] Then, the mask on the anode collector was removed and the
side faces of the cathode 4 and the diffusion layer 5 were masked.
Thereafter, a conductive paint was poured in the anode collector
with nickel metal powders being used as a filler and polyvinylidene
fluoride being used as a binder, and was electrically connected to
the side faces of the adjacent cathode 4 and diffusion layer 5.
[0113] Glass fiber with a porosity of 85% was filled into the
cylinder of the obtained cylindrical fuel cell unit as the liquid
holding material 14, and the 2 mm thick polypropylene-made lids 12
and 13 having the fuel discharge port 9 and the supply port 10 each
having an outside diameter of 3 mm and an inside diameter of 2 mm
were welded to the top and bottom of the cylinder, respectively, to
provide airtightness. An anode terminal 18 was pulled out of the
anode terminal strip 15, and a cathode terminal 19 was pulled out
of the lower end portion of the cathode collector 7. The obtained
cylindrical fuel cell unit formed by connecting three single cells
in series was a single cell having a fuel filling volume of about
1.8 cm.sup.3 and a power generation effective area of about 5
cm.sup.2. The voltage of a load current of 0.8A at 55.degree. C.,
which was measured by filling 10 wt % of aqueous solution of
methanol as a liquid fuel, was about 0.98 V as indicated by curve
71 in FIG. 11.
[0114] For the cylindrical fuel cell unit having such a
construction, as in the case of the second embodiment, the joining
process for the cell members can be made easy, and the output
voltage of unit cell can be made high. Also, since the output
voltage of fuel cell unit can be made high, the degree of freedom
of selecting the height of cell can be provided. Especially in the
case where the load current is relatively small, and a high voltage
is needed, this construction enables the power source to be
manufactured in a compact manner.
[0115] The following will be a description of a fourth embodiment
of the present invention.
[0116] An outside construction of a high-voltage fuel cell unit
having a square tubular construction, which uses aqueous solution
of methanol as a fuel, in accordance with still another embodiment
of the present invention is shown in FIG. 9A, and an outside
construction thereof before the polyethylene mash 20 for tightening
the fuel cell unit is mounted is shown in FIG. 9B. Also, one
sectional configuration of the support 1 is shown in FIG. 10A, and
another sectional configuration adjacent to the above is shown in
FIG. 10B.
[0117] As shown in FIG. 9B, the hollow support 1 of the fuel cell
unit was formed of a polypropylene-made square tube having an
outside dimensions of 10 mm.times.10 mm.times.115 mm and a
thickness of 1 mm. On each of four outside surfaces of the square
tube was provided a cell mounting portion having an engraved
construction measuring 9 mm.times.104 mm and 200 .mu.m deep, and as
shown in FIGS. 10A and 10B, a conductive carbon paint with a
thickness of about 50 .mu.m was applied onto this surface and over
the anode end face with polyvinylidene fluoride being used as a
binder, by which the anode collector 6 was formed.
[0118] Next, a region of 5 mm.times.100 mm in the cell mounting
portion was made a current carrying portion, and there was provided
the porous section 8 so that through holes with a diameter of about
0.5 mm were formed with a porosity of about 65%. Glass fiber with a
porosity of 85% was filled into the square tube as the liquid
holding material 14, and the 2 mm thick lids 12 and 13 having the
fuel discharge port 9 and the supply port 10, respectively, were
mounted to provide airtightness.
[0119] By the same method as that of the second embodiment, a
platinum-ruthenium carrying carbon catalyst for anode catalyst, a
platinum carrying carbon powder catalyst for cathode catalyst, and
Nafion membrane 117 (manufactured by Du Pont) with a thickness of
50 .mu.m for electrolyte membrane were used, and the anode 3 having
dimensions of 5 mm.times.100 mm and a thickness of 25 .mu.m and the
cathode 4 having a thickness of 15 .mu.m were lapped on both
surfaces of the electrolyte membrane 2 having dimensions of 9
mm.times.104 mm, by which the membrane electrode assembly was
manufactured.
[0120] Next, the peripheral electrolyte membrane and the cell
mounting portion of the membrane electrode assembly were bonded to
each other with the silicone liquid gasket 16 so that the anode
side of the membrane electrode assembly was in contact with the
cell mounting portion of the hollow support. The diffusion layer 5
that was the same as that used in the second embodiment and a
cathode collector 7a of a shape such that a tab 7b was provided at
the end that was manufactured by the same method as that of the
second embodiment were lapped on the surface of the mounted
cathode, and the outer peripheral portion was fixed with the
polyethylene-made tightening mesh 20 via the silicone liquid gasket
16 provided between the electrolyte membrane 2 and the cell
mounting portion.
[0121] As shown in FIG. 10B, the tab portions of the cathode
collectors 7 mounted on four surfaces of the hollow support were
lapped on each other in the vertically reverse direction
alternately, and each tab was bonded to the adjacent anode
collector 7, by which a cell group consisting of four single cells
connected in series was formed.
[0122] The obtained tubular fuel cell unit had a power generation
effective area of about 5 cm.sup.2, and the fuel cell unit using 10
wt % of aqueous solution of methanol as a liquid fuel exhibited
performance of voltage of 1.3 V at an output current of 0.5A as
indicated by curve 72 in FIG. 11 at an operating temperature of
60.degree. C. For such a construction of the square tubular fuel
cell unit, since each square tube forms a cell independently, the
joining process for the cell members can be made easy, and the
output voltage of unit cell can be made high. Also, since the
output voltage of fuel cell unit can be made high, the degree of
freedom of selecting the height of cell can be provided. Especially
in the case where the load current is relatively small, and a high
voltage is needed, this construction enables the power source to be
manufactured in a compact manner.
[0123] As comparative example 1, one in-plane construction and the
longitudinal cross section of a separator in accordance with the
conventional construction is shown in FIG. 12A, and the other
in-plane construction and the longitudinal cross section is shown
in FIG. 12B. Also, a laminating configuration of a cell is shown in
FIG. 13, and a construction of a cell holder is shown in FIG. 14.
Further, a construction of a power source system in which fourteen
single cells are laminated in series and a fuel tank is provided is
shown in FIG. 15.
[0124] As the separator, a graphitized carbon plate measuring 50
mm.times.21 mm and 3 mm thick was used. At the bottom of the
separator 81 was provided an internal manifold 82 having dimensions
of 5 mm.times.15 mm. As shown in FIG. 12A, grooves each measuring 1
mm wide.times.0.8 mm deep.times.39 mm long were formed at intervals
of 2 mm to form ribs 21, and fuel supply grooves connecting the
manifold 82 to the upper side face of the separator 81 were
provided. As shown in FIG. 12B, in the direction perpendicular to
the above in the other surface, grooves each measuring 1 mm
wide.times.1.4 mm deep.times.21 mm long were formed at intervals of
2 mm to form ribs 21, and oxidizer supply grooves connecting the
side faces of the separator 81 to each other were provided. Next,
Nafion 117 measuring 50 mm.times.21 mm and 50 .mu.m thick serving
as the electrolyte membrane was provided with a manifold hole 86,
and the anode with a thickness of 25 .mu.m was applied onto one
surface of the generator section measuring 36 mm.times.14 mm and
the cathode with a thickness of 15 .mu.m was applied onto the other
surface thereof by the same method as that of the second
embodiment, by which a membrane electrode assembly 91 was
manufactured.
[0125] As the anode catalyst, a catalyst in which a
platinum-ruthenium alloy catalyst was carried in a carbon carrier
was used. As the cathode catalyst, a catalyst in which platinum was
carried in a carbon carrier was used. The quantity of platinum for
anode was about 1.3 mg/cm.sup.2, and the quantity of ruthenium
therefor was about 0.65 mg/cm.sup.2. The quantity of platinum for
cathode was about 0.8 mg/cm.sup.2.
[0126] Then, a 250 .mu.m thick polyethylene terephthalate liner 92,
which had the same size as that of the separator 81 and was
provided with a manifold hole 86 and a generator section hole 85,
and a 400 .mu.m thick neoprene gasket 16 were manufactured. Also,
the diffusion layer 5 was manufactured by the same method as that
of the first embodiment.
[0127] Next, a pulpboard-made sucking-up element 94 composed of a
portion 88 embedded in the groove on the fuel electrode side of the
separator 81 and a portion 87 embedded in the manifold thereof was
manufactured. The separator 81, sucking-up element 94, liner 92,
gasket 93, membrane electrode assembly 91, diffusion layer 5, liner
92, and separator 81 were piled up in that order as a unit, and
fourteen units were laminated and pressed under a pressure of about
5 kg/cm.sup.2 to form a layer-built cell 23 as shown in FIG. 15.
This layer-built cell 23 was fixed by being tightened with
tightening bands 17 of fluorine-based rubber (Viton, manufactured
by Du Pont) via SUS316 cell holders 105 having a construction shown
in FIG. 14 as shown in FIG. 15A. The fuel tank 102 was manufactured
which was made of polypropylene, had outside dimensions of 50 mm
high.times.21 mm long.times.21 mm wide, and had side walls with a
thickness of 0.3 mm.
[0128] As shown in FIG. 15B, in the center of the fuel tank 102,
there was provided the screwed lid type fuel resupply port 103
provided with a function for selectively permeating gas by mounting
a porous polytetrafluoroethylene membrane having a construction
shown in FIG. 5, and the fuel tank was filled with aqueous solution
of methanol used as the fuel 104.
[0129] The manufactured layer-built cell was connected to the fuel
tank 102 in such a manner as shown in FIG. 15B, by which a power
source having a construction as shown in FIG. 15A was manufactured.
The obtained power source had dimensions of approximately 50 mm
high.times.72 mm long.times.21 mm wide and a power generation area
of about 5 cm.sup.2, and was provided with the fuel tank having a
capacity of about 20 cm.sup.3.
[0130] This power source exhibited a voltage of 2.5 V at a load
current of 0.8 A at an operating temperature of 60.degree. C., and
the voltage in the case where power was generated while air is fed
with a fan to the entire hole portion of the power source side wall
formed of grooves on the air electrode side of separator was 4.1
V.
[0131] The reason for this is probably that the supply of oxygen
due to sufficient air diffusion is insufficient in the groove
construction on the air electrode side of separator. The volumetric
output density of this power source was about 26 W/l when no fan
was used, and was about 43 W/l when a fan was used. When the fuel
tank was filled with 19 ml of 10 wt % aqueous solution of methanol,
and the power source was operated at a load current of 0.8 A at an
operating temperature of 60.degree. C. with the use of a fan, the
voltage decreased suddenly after the output voltage of 4.0 V
continued for about 25 minutes. Therefore, the volumetric energy
density provided by one charge of 10 wt % aqueous solution of
methanol was 18 Wh/l when a fan was used.
[0132] Next, description will be given with reference to FIG. 17
showing a construction of a high-voltage power source using a
separator as comparative example 2 and FIG. 16 showing a
construction of a cell holder.
[0133] The used separator, sucking-up element, liner, gasket,
membrane electrode assembly, and diffusion layer, which were
components of cell, were made of the same material with the same
size as that of comparative example 1, and two sets of layer-built
cells 23 were manufactured by the same procedure so that the unit
cell consisted of twenty-one cells were provided.
[0134] The two sets of layer-built cells were inserted so that the
cell bottom face was in contact with a cell fixing plate 106 of the
cell holder 105 shown in FIG. 16, and were fixed with the
tightening bands 17 of fluorine-based rubber as in the case of
comparative example 1. The fuel tank 102 was made of polypropylene,
had outside dimensions of 50 mm high.times.21 mm long.times.35 mm
wide, and had side walls with a thickness of 0.3 mm.
[0135] As shown in FIG. 17, in the center of the fuel tank 102,
there was provided the screwed lid type fuel resupply port 103
provided with a function for selectively permeating gas by mounting
a porous polytetrafluoroethylene membrane having a construction
shown in FIG. 5. The manufactured layer-built cell was connected to
the fuel tank in the same way as that of comparative example 1 as
shown in FIG. 17, and two sets of layer-built cells were connected
to each other in series, by which a power source was formed.
[0136] The obtained power source had dimensions of approximately
110 mm high.times.110 mm long.times.21 mm wide and a power
generation area for single cell of about 5 cm.sup.2, and was
provided with two fuel tanks 102 each having a capacity of about 34
cm.sup.3. This power source exhibited a voltage of 7.4 V at a load
current of 0.8 A at an operating temperature of 60.degree. C., and
the voltage in the case where power was generated while air is fed
with a fan to the entire hole portion of the power source side wall
formed of grooves on the air electrode side of separator was 13.1
V. The reason for this is probably that the supply of oxygen due to
sufficient air diffusion is insufficient in the groove construction
on the air electrode side of separator at the time when the power
source is loaded.
[0137] The volumetric output density of this power source was about
23 W/l when no fan was used, and was about 41 W/l when a fan was
used. When the two fuel tanks were filled with a total of 150
cm.sup.3 of 10 wt % aqueous solution of methanol, and the power
source was operated at a load current of 0.8 A at an operating
temperature of 60.degree. C. with the use of a fan, the voltage
decreased suddenly after the output voltage of 13 V continued for
about 30 minutes. Therefore, the volumetric energy density provided
by one charge of 10 wt % aqueous solution of methanol was 20 Wh/l
when a fan was used.
[0138] The following will be a description of a fifth embodiment of
the present invention. A construction of a power source in which
fourteen fuel cell units each filled with the liquid holding
material 14 are combined in series, the fuel cell unit being
manufactured by the method shown in the first embodiment as a power
source system formed of square tubular methanol fuel cell units in
accordance with one embodiment of the present invention, is shown
in FIG. 18A, and a sectional configuration for illustrating the
connection of the fuel cell unit with the fuel tank is shown in
FIG. 18B.
[0139] The fourteen fuel cell units are stored in series in the
well-ventilated polyethylene-made cell holder 105 having a
construction shown in FIG. 19. The fuel tank 102 is made of
polypropylene, has outside dimensions of 50 mm high.times.72 mm
long.times.15 mm wide, and has side walls with a thickness of 0.3
mm.
[0140] As shown in FIG. 12B, the fuel supply port 10 and the
discharge port 9 of the fuel cell unit 101 are connected to the
upper and lower parts of the side wall with the fuel tank 102 being
a platform in an airtight manner. In the center on the top face of
the tank, there is provided the screwed lid type fuel resupply port
103 provided with a function for selectively permeating gas by
mounting a porous polytetrafluoroethylene membrane having a
construction shown in FIG. 5, and the fuel tank is filled with 10
wt % of aqueous solution of methanol used as the fuel 104.
[0141] The cathode terminal of the fuel cell unit mounted in the
cell holder 105 is connected to the adjacent anode terminal, and
both ends of fourteen fuel cell units connected in series are used
as power source terminals. The obtained power source has dimensions
of approximately 50 mm high.times.72 mm long.times.20 mm wide and
is provided with the fuel tank having a capacity of about 50
cm.sup.3. This power source exhibited a voltage of 4.2 V at a load
current of 0.8 A at an operating temperature of 65.degree. C. The
volumetric output density of this power source was about 47 W/l.
When the fuel tank was filled with 50 cm.sup.3 of 10 wt % aqueous
solution of methanol, and the power source was operated at a load
current of 0.8 A at an operating temperature of 60.degree. C.,
power generation was able to be continued steadily for about 60
minutes at an output voltage of 4.2 V. Therefore, the volumetric
energy density provided by one charge of 10 wt % aqueous solution
of methanol was 47 Wh/l.
[0142] According to this embodiment, since the fourteen fuel cell
units could be mounted in a compact manner, the capacity of fuel
tank was able to be increased as compared with comparative example
1 providing almost the same volumetric output density in the cell
construction using the conventional separator, and the volumetric
energy density was about 2.5 times. Since the fuel cell units were
mounted at intervals such that air, which served as an oxidizer,
could be diffused sufficiently, power was able to be generated
without the use of a fan for assisting the air supply unlike the
power source of comparative example 1.
[0143] The following will be a description of a sixth embodiment of
the present invention. A construction of a power source in which
fourteen fuel cell units combined in series are arranged in two
rows in parallel, the fuel cell unit being manufactured by the
method shown in the second embodiment as a power source system
formed of cylindrical methanol fuel cell units in accordance with
another embodiment of the present invention, is shown in FIG. 20A,
and a sectional configuration for illustrating the connection of
the fuel cell unit with the fuel tank is shown in FIG. 20B.
[0144] The fuel cell units are stored in the cell holder 105 having
a construction shown in FIG. 21 so that fourteen units combined in
series are arranged in two rows in parallel. The fuel tank 102 is
made of polypropylene, has outside dimensions of 70 mm
high.times.76 mm long.times.22 mm wide, and has a construction
having a platform construction with side walls 0.3 mm thick. As
shown in FIG. 20B, the platform of the fuel tank 102 is filled with
the liquid holding material 14. On the top face of the tank, there
is provided the screwed lid type fuel resupply port 103 provided
with a function for selectively permeating gas by mounting a porous
polytetrafluoroethylene membrane having a construction shown in
FIG. 5, and the fuel tank is filled with aqueous solution of
methanol used as the fuel.
[0145] As shown in FIG. 20B, the fuel supply port 10 of each of the
fuel cell units 101 is connected to the fuel tank 102, which serves
as a platform, in an airtight manner, and above the fuel cell unit
group, an exhaust tank 110 is mounted so as to be connected to the
discharge port 9 of each of the fuel cell units in an airtight
manner. The exhaust tank 110 is made of polypropylene, has outside
dimensions of 10 mm high.times.76 mm long.times.8 mm wide, and has
side walls with a thickness of 0.3 mm. On the top face of the
exhaust tank 110, there is provided a screwed lid type exhaust port
111, which is a port for selectively permeating gas, in which a
porous polytetrafluoroethylene membrane having a construction shown
in FIG. 5 is mounted.
[0146] The cathode terminal of each of the fuel cell units mounted
in the cell holder 105 is connected to the adjacent anode terminal,
by which the fuel cell units are connected electrically so that
fourteen units combined in series are arranged in two rows in
parallel. The obtained power source has dimensions of approximately
70 mm high.times.76 mm long.times.22 mm wide and is provided with
the fuel tank having a capacity of about 55 cm.sup.3. This power
source exhibited a voltage of 3.6 V at a load current of 1.5 A at
an operating temperature of 60.degree. C. The volumetric output
density of this power source was about 50 W/l.
[0147] When the fuel tank was filled with 55 cm.sup.3 of 10 wt %
aqueous solution of methanol, and the power source was operated at
a load current of 1.5 A at an operating temperature of 60.degree.
C., power generation was able to be continued for about 20 minutes
at an output voltage of 3.5 V.
[0148] According to this embodiment, since the twenty-eight fuel
cell units could be mounted in a compact manner, the power
generation area was able to be increased as compared with the cell
construction of comparative example 1 using the conventional
separator, and a large load current was able to be obtained. Since
the fuel cell units were mounted at intervals such that air, which
served as an oxidizer, could be diffused sufficiently, power was
able to be generated without the use of a fan for assisting the air
supply unlike the power source of comparative examples 1 and 2.
[0149] The following will be a description of a seventh embodiment
of the present invention. An outside construction of a power source
in which fourteen fuel cell units are combined in series, the fuel
cell unit being manufactured by the method shown in the third
embodiment as a power source system formed of high-voltage
cylindrical methanol fuel cell units in accordance with still
another embodiment of the present invention, is shown in FIG. 22A,
and a sectional configuration of the connection of the fuel cell
unit with the fuel tank, which serves as a platform, is shown in
FIG. 22B.
[0150] Fourteen fuel cell units are mounted in the well-ventilated
polyethylene-made cell holder 105 having the same construction as
described in the fifth embodiment, and are electrically connected
in series. The fuel tank 102, which serves as a platform, has
outside dimensions of 100 mm high.times.120 mm long.times.13 mm
wide, and is constructed by side walls with a thickness of 0.3 mm.
On the top face of the fuel tank 102, there is provided the screwed
lid type fuel resupply port 103 provided with a function for
selectively permeating gas by mounting a porous
polytetrafluoroethylene membrane having a construction shown in
FIG. 5, and the fuel tank is filled with aqueous solution of
methanol used as the fuel. The side wall of the fuel tank 102 is
mounted in an airtight manner via the fuel supply port 10 and the
discharge port 9 of the fuel cell unit as shown in FIG. 22B. The
obtained power source has dimensions of approximately 100 mm
high.times.120 mm long.times.21 mm wide and is provided with the
fuel tank having a capacity of about 145 cm.sup.3. This power
source exhibited a voltage of 13.3 V at a load current of 0.8 A at
an operating temperature of 65.degree. C. The volumetric output
density of this power source was about 42 W/l. When the fuel tank
was filled with 145 cm.sup.3 of 10 wt % aqueous solution of
methanol, and the power source was operated at a load current of
0.8 A at an operating temperature of 60.degree. C., power
generation was able to be continued steadily for about 65 minutes
at an output voltage of 13.2 V. Therefore, the volumetric energy
density provided by one charge of 10 wt % aqueous solution of
methanol was 45 Wh/l.
[0151] According to this embodiment, since the fourteen fuel cell
units could be mounted in a compact manner, the capacity of fuel
tank was able to be increased as compared with comparative example
2 in which the power source of almost the same size was
manufactured in the cell construction using the conventional
separator, and the volumetric energy density was about two times.
Since the fuel cell units were mounted at intervals such that air,
which served as an oxidizer, could be diffused sufficiently, power
was able to be generated without the use of a fan for assisting the
air supply unlike the power source of comparative example 2.
[0152] The following will be a description of an eighth embodiment
of the present invention. An outside construction of a power source
in which seven fuel cell units are combined in series, the fuel
cell unit being manufactured by the method shown in the fourth
embodiment as a power source system formed of high-voltage square
tubular fuel cell units in which aqueous solution of methanol is
used as a fuel, is shown in FIG. 23A, and a sectional configuration
of the connection of the fuel cell unit with the fuel tank, which
serves as a platform, is shown in FIG. 23B.
[0153] Seven fuel cell units 101 are mounted in the well-ventilated
polyethylene-made cell holder 105 having the same construction as
described in the fifth embodiment, and are electrically connected
in series. The fuel tank 102 is made of polypropylene, has outside
dimensions of 130 mm high.times.80 mm long.times.22 mm wide, and is
constructed so as to have a platform for mounting the cells. The
platform of the fuel tank 102 is filled with the liquid holding
material 14 as shown in FIG. 23B. On the top face of the fuel tank,
there is provided the screwed lid type fuel resupply port 103
provided with a function for selectively permeating gas by mounting
a porous polytetrafluoroethylene membrane having a construction
shown in FIG. 5, and the fuel tank is filled with aqueous solution
of methanol used as the fuel. Each of the fuel cell units 101 and
the platform of the fuel tank 102 are connected to each other in an
airtight manner via the fuel supply port 10 of the fuel cell unit
101 in the same way as that of the sixth embodiment. Above the fuel
cell unit group, the exhaust tank 110 is mounted via the discharge
port 9 of each of the fuel cell units 101 in an airtight manner.
The exhaust tank 110 is made of polypropylene, has outside
dimensions of 10 mm high.times.80 mm long.times.10 mm wide, and has
side walls with a thickness of 0.3 mm.
[0154] On the top face of the exhaust tank 110, there is provided
the screwed lid type exhaust port 111, which is a port for
selectively permeating gas, in which a porous
polytetrafluoroethylene membrane having a construction shown in
FIG. 5 is mounted. The obtained power source has dimensions of
approximately 130 mm high.times.80 mm long.times.22 mm wide and is
provided with the fuel tank having a capacity of about 110
cm.sup.3. This power source exhibited a voltage of 8.5 V at a load
current of 0.8 A at an operating temperature of 60.degree. C. The
volumetric output density of this power source was about 30 W/l.
When the fuel tank was filled with 110 cm.sup.3 of 10 wt % aqueous
solution of methanol, and the power source was operated at a load
current of 0.8 A at an operating temperature of 60.degree. C.,
power generation was able to be continued steadily for about 75
minutes at an output voltage of 8.5 V.
[0155] Therefore, the volumetric energy density provided by one
charge of 10 wt % aqueous solution of methanol was 37 Wh/l.
According to this embodiment, since the seven fuel cell units in
which four single cells were connected in series could be mounted
in a compact manner, the capacity of fuel tank was able to be
increased as compared with the case in which the power source was
manufactured in the cell construction using the conventional
separator, and the volumetric energy density was about two times.
Since the fuel cell units were mounted at intervals such that air,
which served as an oxidizer, could be diffused sufficiently, power
was able to be generated without the use of a fan for assisting the
air supply unlike the power source of comparative examples 1 and
2.
[0156] The following will be a description of a ninth embodiment of
the present invention. An outside construction of a power source
formed of a cylindrical fuel cell unit, which uses aqueous solution
of methanol as a fuel, is shown in FIG. 24A, and a sectional
configuration thereof is shown in FIG. 24B.
[0157] A cylinder which is made of stainless steel SUS316, measures
5.6 mm in outside diameter, 5.3 mm in inside diameter, and 47 mm in
length, has a closed bottom, and is provided with a 5 mm long screw
type connector element 24 above the cylinder is used as the hollow
cylindrical support 1. The porous section 8 was provided over a 36
mm width on the outside wall of the cylinder by forming through
holes with a diameter of about 0.5 mm so that the porosity was
about 70%. On the other hand, a Nafion 117 membrane of 17.5
mm.times.42 mm was used as the electrolyte membrane 2. A
platinum-ruthenium catalyst with carbon carrier was applied onto
one electrolyte membrane surface by the same method as that of the
second embodiment so that its size was 16 mm.times.36 mm and its
thickness was 20 .mu.m to form the anode electrode 3, and a
substance produced by adding polytetrafluoroethylene powders with
60% of catalyst weight to a platinum catalyst with carbon carrier
as a water repellant and by mixing them was applied onto the
surface opposite to the surface onto which anode was applied so
that its size was 16 mm.times.36 mm and its thickness was 15 .mu.m
to form the cathode electrode 4, by which a membrane electrode
assembly was manufactured. The silicone liquid gasket 16 was
applied to a potion with a width of 3 mm of electrolyte membrane
exposed to both ends of a long side of the obtained membrane
electrode assembly. While the liquid gasket 16 was wound so that
the cathode face lapped on the porous section 8 of the hollow
support 1 and was tightened from the outer periphery, Nafion
alcohol solution concentrated to 30 wt % in advance was applied to
a joint portion in which the electrolyte membrane 2 exposed at both
ends of the short side was in contact in the lengthwise direction
of the cylindrical support, and the alcohol solution was dried to
effect bonding.
[0158] The exposed face of the electrolyte membrane 2 corresponding
to the portion in which the gasket 16 was applied at the upper and
lower ends of the membrane electrode assembly mounted on the hollow
cylindrical support was fixed with the rubber-based tightening band
17, and on the outer peripheral surface of the cathode 4, the
porous cathode collector 7 in which a copper-made mesh was coated
with a conductive carbon paint with polyvinylidene fluoride being
used as a binder was tightened and fixed. The fixed cathode
collector 17 was used as a cathode terminal, and the metallic
hollow cylindrical support was used as an anode terminal. The
obtained fuel cell unit had a power generation area of about 5.7
cm.sup.2 and a hollow cylinder volume of about 0.8 cm.sup.3. The
hollow cylinder was filled with 10 wt % of aqueous solution of
methanol, and the performance of the fuel cell unit was evaluated
at a temperature of about 60.degree. C. As a result, the output
voltage was 0.36 V at a load current of 0.8 A.
[0159] Since the fuel cell unit in accordance with this embodiment
is formed of a single cell, the hollow support can be formed of a
corrosion resistant metallic material. Therefore, the hollow
support has a function of the anode collector and the anode
terminal, so that the construction of fuel cell unit can be made
simple.
[0160] The configuration of a power source will be described with
reference to FIG. 25A showing an outside construction of a power
source in which forty-two cylindrical fuel cell units manufactured
in this embodiment are arranged in series and FIG. 25B showing a
sectional construction of the connection of the fuel cell unit with
a fuel tank serving as a platform. The fuel tank 102 was made of
vinyl chloride, had outside dimensions of 65 mm high.times.43 mm
wide.times.50 mm long, and had a construction in which the bottom
plate had a thickness of 5 mm and the other walls had a thickness
of 1 mm. On the top face of the fuel tank, there were provided two
screwed lid type fuel resupply ports 103 provided with a function
for selectively permeating gas by mounting a porous
polytetrafluoroethylene membrane having a construction shown in
FIG. 5, and the fuel tank was filled with aqueous solution of
methanol used as the fuel 104. A screw type mount port was provided
at the bottom of the fuel tank 102, and was connected to the
connector element 24 of the fuel cell unit 101 in an airtight
manner.
[0161] The power source was constructed so that a group of the fuel
cell units 101 mounted on the fuel tank 102 and a base plate 112
having outside dimensions of 3 mm wide.times.50 mm long.times.3 mm
thick were fixed by a support member 113. The obtained power source
approximately measured 111 mm high.times.43 wide.times.50 mm long,
had a maximum fuel filling capacity of about 150 cm.sup.3 and a
power generation area of 5.7 cm.sup.2, and was constructed by
forty-two fuel cell units arranged in series. When this power
source was filled with 150 cm.sup.3 of 10 wt % aqueous solution of
methanol as a fuel, and was operated at a load current of 1 A at a
temperature of about 60.degree. C., power generation was continued
for about 50 minutes at an output voltage of 13 V. Therefore, the
volumetric output density of this power source was 54 W/l, and the
volumetric energy density provided by one charge of 10 wt % aqueous
solution of methanol was 45 Wh/l.
[0162] Since this power source has the fuel tank at the upper part
thereof, fuel is always filled into the fuel cell units. Therefore,
this power source has a characteristic of no need for the liquid
holding material for fuel, which has been described in the fifth
and sixth embodiments, to be filled. In this embodiment as well,
the volumetric energy density could be two times or more as
compared with the cell of comparative example 2. Since the fuel
cell units were mounted at intervals such that air, which served as
an oxidizer, could be diffused sufficiently, power was able to be
generated without the use of a fan for assisting the air supply
unlike the power source of comparative example 2.
[0163] The following will be a description of a tenth embodiment of
the present invention. A power source system formed of cylindrical
fuel cell units, which use aqueous solution of methanol as a fuel,
is shown in FIG. 26A, and a sectional configuration thereof is
shown in FIG. 26B. FIG. 27 is a sectional view showing a state in
which an auxiliary fuel tank is connected to a fuel tank.
[0164] The fuel cell units 101 are stored in the cell holder 105
having a construction as shown in FIG. 21 so that fourteen cell
units combined in series are arranged in two rows. The fuel tank
102 is formed of a platform which is made of polypropylene and has
outside dimensions of 20 mm high.times.76 mm long.times.30 mm wide
and side walls having a thickness of 1 mm. The platform of the fuel
tank 102 is filled with the liquid holding material 14 as shown in
FIG. 26B, and the platform of an auxiliary fuel tank 107 is
provided with a connector portion 24 having a detachable
construction as shown in FIG. 27. The auxiliary fuel tank 107 is
made of polypropylene and has outside dimensions of 49 mm
high.times.76 mm long.times.22 mm wide and side walls having a
thickness of 1 mm. On the top face of the auxiliary fuel tank,
there is provided the screwed lid type fuel resupply port 103
provided with a function for selectively permeating gas by mounting
a porous polytetrafluoroethylene membrane having a construction
shown in FIG. 5, and the auxiliary fuel tank is filled with aqueous
solution of methanol used as the fuel.
[0165] As shown in FIG. 26B, the fuel supply port 10 of each of the
fuel cell units 101 is connected to the fuel tank 102 serving as a
platform in an airtight manner. Above the fuel cell unit group, the
exhaust tank 110 is mounted so as to be connected to the discharge
port 9 of each of the fuel cell units in an airtight manner. The
exhaust tank 110 is made of polypropylene, has outside dimensions
of 10 mm high.times.76 mm long.times.8 mm wide, and has side walls
with a thickness of 0.3 mm. On the top face of the exhaust tank
110, there is provided the screwed lid type exhaust port 111, which
is a port for selectively permeating gas, in which a porous
polytetrafluoroethylene membrane having a construction shown in
FIG. 5 is mounted. The cathode terminal of each fuel cell unit
stored in the cell holder 105 is connected to the adjacent anode
terminal, by which twenty-eight fuel cell units are connected
electrically. The obtained power source had dimensions of
approximately 70 mm high.times.76 mm long.times.30 mm wide and was
provided with the fuel tank having a capacity of about 31 cm.sup.3,
and the auxiliary fuel tank had a capacity of about 69 cm.sup.3.
When a power generation test was conducted at an operating
temperature of 60.degree. C., the power source exhibited a voltage
of 8.4 V at a load current of 0.8 A. When the auxiliary fuel tank
107 was filled with 65 cm.sup.3 of 10 wt % aqueous solution of
methanol, and the power source was operated at a load current of
1.5 A at an operating temperature of 60.degree. C., power
generation was able to be continued for about 80 minutes at an
output voltage of 3.6 V. Thereafter, when the auxiliary fuel tank
filled with 65 cm.sup.3 of 10 wt % aqueous solution of methanol was
newly replaced, and the power source was operated at a load current
of 1.5 A at an operating temperature of 60.degree. C., power
generation was able to be continued for about 80 minutes at an
output voltage of 3.6 V. The direct methanol fuel cell uses aqueous
solution of methanol as the fuel, and the aqueous solution of
methanol is consumed by permeating the electrolyte membrane in
addition to being consumed as fuel by power generation.
[0166] Because the ratios of the electrolyte membrane permeating
amounts of methanol and water differ depending on the operation
state, the concentration of methanol must be regulated so as to be
in a predetermined range when fuel is newly resupplied to the
tank.
[0167] However, if the capacity of fuel tank connected to the power
source is made relatively low and the power source is operated in
the state in which the auxiliary fuel tank is connected as in this
embodiment, merely by replacing the auxiliary fuel tank filled with
fuel of a fixed concentration as the fuel is consumed, the
long-term use is enable without the regulation of methanol
concentration.
[0168] According to the present invention, in the case where the
required current is relatively small and a high voltage is needed,
the fuel cell unit can be provided with a plurality of generator
sections in which an anode, electrolyte membrane, and cathode are
disposed on the outer peripheral surface of a hollow support, and
the generator sections can be connected to each other in series
with a conductive interconnector. Therefore, a high voltage can be
achieved, and further a small-size fuel cell generator can be
realized.
[0169] Fuel is supplied without any use of a forced supply
mechanism provided in the hollow support by connecting a fuel tank
as a platform. At this time, the hollow support is filled with a
material for holding liquid fuel and sucking it up by the capillary
force, by which fuel is replenished, and the fuel cell unit having
the generator section on the outer peripheral surface of the hollow
support is supplied with an oxidizer by the diffusion of oxygen in
air, so that a simple system without the need for auxiliary
equipment for supplying fuel and oxidizer can be configured.
[0170] Also, by using aqueous solution of methanol with a high
volumetric energy density as a liquid fuel, power generation can be
continued for a long period of time as compared with the case where
hydrogen gas in the tank having the same capacity is used as a
fuel. By successively replenishing fuel, a continuous generator
without the need for charging time unlike the secondary battery can
be realized.
[0171] By using the power source in accordance with the present
invention as a battery charger attached to a cellular phone,
portable personal computer, portable audio and visual equipment,
and other portable information terminals, which are mounted with a
secondary battery, or by using the power source as a directly
incorporated power source without the secondary battery being
mounted, the electronic equipment can be used for a long period of
time, and continuous use of the electronic equipment can be
achieved by the replenishment of fuel.
* * * * *