U.S. patent application number 10/862455 was filed with the patent office on 2004-11-11 for fuel cell power generation equipment and a device using the same.
This patent application is currently assigned to HITACHI, LTD.. Invention is credited to Kamo, Tomoichi, Morishima, Makoto, Ohara, Shuichi.
Application Number | 20040224211 10/862455 |
Document ID | / |
Family ID | 19113251 |
Filed Date | 2004-11-11 |
United States Patent
Application |
20040224211 |
Kind Code |
A1 |
Kamo, Tomoichi ; et
al. |
November 11, 2004 |
Fuel cell power generation equipment and a device using the
same
Abstract
An object of the present invention is to obtain a fuel cell
power generation equipment most suitable for a portable power
source without requiring any auxiliary equipment such as a
separator and a fluid feeder. According to the present invention, a
fuel cell power generation equipment is provided, in which an anode
for oxidizing fuel and a cathode for reducing oxygen are formed
with an electrolyte membrane in between and liquid is used as a
fuel, wherein one or more air vent holes are provided on a wall
surface of a fuel container 1, multiple unit cells having an
electrolyte membrane, an anode and a cathode are mounted on a wall
surface of said fuel container, and the unit cells are electrically
connected each other.
Inventors: |
Kamo, Tomoichi; (Tokai,
JP) ; Ohara, Shuichi; (Hitachi, JP) ;
Morishima, Makoto; (Hitachinaka, JP) |
Correspondence
Address: |
McDermott, Will & Emery
600 13th Street, N.W.
Washington
DC
20005-3096
US
|
Assignee: |
HITACHI, LTD.
Tokyo
JP
|
Family ID: |
19113251 |
Appl. No.: |
10/862455 |
Filed: |
June 8, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10862455 |
Jun 8, 2004 |
|
|
|
10080562 |
Feb 25, 2002 |
|
|
|
Current U.S.
Class: |
429/410 ;
429/454; 429/87 |
Current CPC
Class: |
H01M 8/1097 20130101;
H01M 16/003 20130101; H01M 10/46 20130101; Y02E 60/50 20130101;
Y02E 60/10 20130101; H01M 8/1009 20130101; H01M 8/1011 20130101;
H01M 8/2455 20130101; H01M 2300/0082 20130101; H01M 8/04201
20130101; H01M 4/8631 20130101 |
Class at
Publication: |
429/034 ;
429/032; 429/087 |
International
Class: |
H01M 008/02; H01M
008/10; H01M 002/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 25, 2001 |
JP |
2001-291044 |
Claims
1. (Canceled)
2. A fuel cell power generation equipment in which an anode for
oxidizing fuel and a cathode for reducing oxygen are formed with an
electrolyte membrane in between, and liquid is used as a fuel,
wherein a liquid fuel holding material is filled in contact with an
inner wall surface of a fuel container, one or more air vent holes
having a gas/liquid separation function are provided on a wall
surface of a fuel container, multiple unit cells having an
electrolyte membrane, an anode and a cathode are mounted on said
wall surface of a fuel container, and the unit cells are
electrically connected each other.
3. A fuel cell power generation equipment in accordance with claim
2, wherein a diffusion layer is arranged in contact with an anode
and/or a cathode electrodes.
4. A fuel cell power generation equipment in accordance with claim
2, wherein a liquid fuel holding material filled in a fuel
container is in contact with an anode or a diffusion layer in an
anode side of multiple unit cells mounted on an outer wall surface
of the fuel container.
5. A fuel cell power generation equipment in accordance with claim
2, wherein a liquid fuel container is composed of an electrically
insulating material.
6-8 (Canceled)
9. A fuel cell power generation equipment in accordance with claim
2, wherein a fuel is an aqueous methanol solution.
10-13 (Canceled)
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a fuel cell power
generation equipment comprising an anode, an electrolyte membrane,
a cathode and a diffusion layer, wherein fuel is oxidized at an
anode and oxygen is reduced at a cathode, in particular, compact
type portable power source using liquid fuel such as methanol as a
fuel and mobile electronic devices using this power source.
[0002] Recent progress in electronics technology has contributed to
miniaturizations of telephone set, notebook type personal computer,
audio visual devices or mobile information terminal devices, and
their use is increasingly prevailing as portable electronics
devices.
[0003] Heretofore, these portable electronics devices were driven
by a secondary battery, and have been developed through the
appearances of new type secondary batteries from sealed lead
battery to Ni/Cd, Ni/hydrogen and further Li ion batteries, and
modifications to more compact and light weight types and higher
energy density types. In any of these secondary batteries, cell
active materials to enhance an energy density or cell structure
having a higher capacity have been developed and efforts have been
paid to obtain a power source with longer service time per one
charge.
[0004] However, secondary batteries still have many problems for a
long continuous drive of portable electronics devices because
charging is indispensable after consuming a certain amount of
power, and a charging equipment and a relatively longer charge time
are required. Now, portable electronics devices are progressing
towards devices requiring a power source enabling to supply a
higher output density and a higher energy density, that is, a power
source with a longer continuous service time, in response to an
increasing volume of information and a higher communication speed
in the future. Therefore, a need for a compact power generator (a
micro power generator) serviceable without charging has been
heightened.
[0005] As a power source responding to such requirement, a fuel
cell power source is considered. Since a fuel cell directly
converts electrochemically a chemical energy of fuel to an electric
energy and does not require a driving unit like in a power
generator using an internal combustion engine such as a usual
engine-driven generator, its realization as a compact power
generator device is highly possible. A fuel cell also does not
require to temporary stop an operation of equipment for charging as
in a usual secondary battery, because it can continue a power
generation so long as a fuel is supplied.
[0006] For these requirements, a solid polymer type of fuel cell
(PEFC: Polymer Electrolyte Fuel Cell) is known as a battery with a
high output density, which generates power by oxidizing hydrogen
gas at an anode and reducing oxygen at a cathode using an
electrolyte membrane made of a perfluorocarbon sulfonic acid based
resin.
[0007] To further miniaturize this fuel cell, for example, as
disclosed in JP-A-9-223507, a compact type of PEFC power generation
equipment has been proposed, in which cylindrical batteries
equipped with anode and cathode electrodes at inner and outer
surfaces of hollow fiber type electrolyte are assembled, and
hydrogen gas and air are fed to inner and outer parts of the
cylinder, respectively. However, in the application to a power
source for portable electronics devices, a large volume of fuel
tank should be provided due to a lower volume energy density of a
fuel because the fuel used is hydrogen gas.
[0008] This system also requires auxiliary equipment such as an
equipment to feed a fuel gas or an oxidizing gent gas (such as air)
to a power generation equipment or to humidify electrolyte membrane
to maintain the cell performance, which complicates a composition
of power generation system and thus the system is not sufficient to
attain miniaturization.
[0009] In order to raise a volume energy density of fuel, it is
effective to use a liquid fuel and to eliminate auxiliary equipment
to feed a fuel or an oxidizing agent to cell to obtain a simple
composition. Such example has been proposed in JP methanol and
water as fuels.
[0010] This power generation equipment has an anode which is
arranged in a manner to contact with outer wall side of a liquid
fuel container,via a material to feed liquid fuel by a capillary
force, and is further composed of a solid polymer electrolyte
membrane and a cathode connected sequentially.
[0011] This type of power generating equipment features in a simple
composition not to require any auxiliary equipment to feed a fuel
and an oxidizing agent thanks to a diffusive feed of oxygen to
outer surface of a cathode which is exposed to ambient air, and
also in a requirement for an electrical connection only without any
separator as a connecting part for unit cells when multiple cells
are combined in series.
[0012] However, since an output voltage per unit cell of DMFC under
load is 0.3 to 0.4 V, DMFC requires a connection of cells in series
by using multiple fuel tanks attached to a fuel cell to respond to
a voltage required by portable electronics. Miniaturization of
power generation equipment also requires increased number of cells
in series and reduction of a fuel container volume per unit cell,
remaining a problem that fuel container is divided into multiple
containers in response to a number of cells in series.
[0013] In addition, a continuous service becomes difficult unless
some discharging mechanism is realized for a gas generated in a
liquid fuel tank by an oxidation reaction at an anode with an
operation of this acid type electrolyte fuel cell.
[0014] An object of the present invention is to provide a fuel cell
power generation equipment easily and continuously serviceable by
feeding a fuel, without charging after consumption of a certain
amount of power like a secondary battery, and a system using a fuel
having a high volume energy density.
[0015] Another object of the present invention is to provide a
compact power source most suitable for portable use as well as
portable electronics devices using the same, wherein a fuel cell
power generation equipment is composed of unit cells comprising an
anode, an electrolyte membrane and a cathode laminated with a
separator having a conductive fluid channel structure in between to
obtain a specified voltage, the power source being a compact fuel
cell without having an auxiliary equipment such as a fluid feeding
mechanism instead of a conventional fuel cell having a fluid
feeding mechanism which enforces passing through of a fuel and an
oxidizing agent gas, enabling feeding a liquid fuel to each unit
cell in any position of power source, and having a discharging
function for a gas oxidized and generated in an anode from a fuel
container.
SUMMARY OF THE INVENTION
[0016] Summary of the present invention which attains the above
described objects is as follows.
[0017] A fuel cell power generation equipment is provided in which
an anode to oxidize fuel and a cathode to reduce oxygen are formed
with an electrolyte membrane in between and a liquid is used as a
fuel, wherein the equipment has one or more air venting hole in a
wall surface of a fuel container, and multiple unit cells having an
electrolyte membrane, an anode and a cathode are mounted on said
wall surface of fuel container, and the unit cells are electrically
connected each other.
[0018] A liquid fuel container is used as a platform, and multiple
unit cells, consisting of an anode, a cathode and an electrolyte
membrane, are mounted on its outer wall surface.
[0019] In particular, in the case when a relatively low current and
a high voltage are required, a high voltage can be obtained by
arranging multiple unit cells consisting of an anode, an
electrolyte membrane and a cathode on an outer circumferential
surface of a fuel container and connecting each unit cell in series
or in combination of series and parallel with conductive
interconnectors.
[0020] A fuel can be fed without installing auxiliary equipment to
compulsively feed fuel to each unit cell, by connecting a fuel
container as a platform. In this case, feeding of a fuel is further
stabilized by retaining liquid fuel in a liquid fuel container and
filling a material to suck up fuel by capillary force.
[0021] On the other hand, an oxidizing agent is fed by a diffusion
of oxygen in air to each unit cell having a power generation part
at outer wall surface of the liquid fuel container. A longer power
generation can be continued by using a liquid fuel having a high
volume energy density such as aqueous methanol solution as a fuel
in comparison with the case when hydrogen gas is used as a fuel in
the same volume of container.
[0022] By using a power source comprising a fuel cell in accordance
with the present invention as a battery charger which is used to
charge up secondary battery mounted cellular phone, portable
personal computer, portable audio, visual equipment and other
portable information terminals, during a temporary stop operation,
or by using the power source directly as a built-in power source
without mounting a secondary battery, it becomes possible to extend
service times of these electronics devices and use continuously by
feeding a fuel.
[0023] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a drawing of cross-sectional structure of a fuel
container of the present invention.
[0025] FIG. 2 is a schematic drawing showing a composition of an
electrode/electrolyte membrane assembly of the present
invention.
[0026] FIG. 3 is a cross-sectional drawing of a fuel cell fixing
plate of the present invention.
[0027] FIG. 4A and FIG. 4B are drawings of cross-sectional
structures of an air vent hole and a container fitting part of the
present invention.
[0028] FIG. 5 is a composition drawing of a mounting part of a fuel
cell of Example 1.
[0029] FIG. 6 is an appearance drawing of a fuel cell power
generation equipment of Example 1.
[0030] FIG. 7A and FIG. 7B are appearance and cross-sectional
drawings of a separator of Comparative Example 1.
[0031] FIG. 8 is a composition drawing of a laminated composition
of a fuel cell of Comparative Example 1.
[0032] FIG. 9 is a composition drawing of an outer plate of a high
voltage type rectangular tube shaped unit cell of the present
invention.
[0033] FIG. 10A and FIG. 10B are drawings showing an appearance
structure of a power source and a connection of power source/fuel
tank of Comparative Example 1.
[0034] FIG. 11 is a composition drawing of electrode/electrolyte
membrane assembly of Example 1.
[0035] FIG. 12 is an appearance drawing of a fuel cell power
generation equipment of Example 1.
[0036] FIG. 13 is a cross-sectional drawing of a fuel cell power
generation equipment of Example 1.
[0037] FIG. 14 is an appearance drawing of a fuel cell power
generation equipment of Comparative Example 2.
[0038] FIG. 15 is a cross-sectional drawing of a fuel container of
Example 2.
[0039] FIG. 16 is a composition drawing of mounting part of a fuel
cell of Example 2.
[0040] FIG. 17 is a cross-sectional drawing of a fuel container of
Example 3.
[0041] FIG. 18 is an appearance drawing of a fuel cell power
generation equipment of Example 4.
[0042] FIG. 19 is an appearance drawing of a fuel cell power
generation equipment of Example 5.
Explanation of Numerals
[0043] 1 . . . fuel container, 2 . . . mounting part of fuel cell,
3 . . . diffusion hole, 4 . . . interconnector, 5 . . . suction
material for liquid fuel, 6 . . . fuel cell terminal, 7 . . .
cathode current collector, 8 . . . fixing plate for fuel cell, 9 .
. . MEA (electrolyte/electrode assembly), 10 . . . gasket, 11 . . .
diffusion layer, 12 . . . aqueous methanol solution, 13 . . . unit
cell, 15 . . . air vent hole, 16 . . . output terminal, 17 . . .
fastening band, 18 . . . fuel retaining layer, 19 . . . mounting
hole of air vent hole, 20 . . . insulation layer, 21 . . .
electrolyte membrane, 22 . . . anode layer, 23 . . . cathode layer,
50 . . . steam separation membrane, 51 . . . air vent tube, 52 . .
. air vent lid, 54 . . . rib part, 81 . . . separator, 82 . . .
manifold, 83 . . . longitudinal cross-section of a separator, 84 .
. . lateral cross-section of a separator, 85 . . . opening part for
power generation, 86 . . . manifold opening part, 87 . . . manifold
insertion part, 88 . . . channel insertion part, 89 . . . rib part,
92 . . . liner, 93 . . . sucking material, 94 . . . laminated cell,
102 . . . fuel tank, 103 . . . mounting part of fuel cell and 105 .
. . cell holder.
DETAILED DESCRIPTION OF THE INVENTION
[0044] Typical embodiments of the present invention are explained
in detail with reference to drawings. FIG. 1 is an example of
cross-sectional structure of a liquid fuel container composing the
present invention.
[0045] Multiple mounting parts 2 for a fuel cell having an
insulating surface are fitted on an outer wall surface of a fuel
container 1, and in a container wall of said mounting part 2 of
fuel cell, a net-like structure, a porous layer or a slit-like
diffusion hole structure 3 through which a liquid fuel sufficiently
permeates is formed in advance.
[0046] An anode side interconnector 4 is formed on a surface of the
mounting part 2 of fuel cell by coating and baking a corrosion
resistant and conductive material to electrically connect to an
adjacent fuel cell. The interconnector 4 has a net-like structure,
a porous layer or a slit-like diffusion hole structure through
which a liquid fuel sufficiently permeates.
[0047] An electrochemically inactive liquid fuel sucking material 5
is mounted on an inner wall surface of a fuel container 1. Fuel
cells mounted on a wall surface of a fuel container are
electrically connected in series or in combination of series and
parallel, and fuel cell terminals 6 of an anode and a cathode are
equipped to take out power from a power generation equipment.
[0048] In a unit cell, as shown in FIG. 2, an anode layer 22 and a
cathode layer 23 are assembled in one piece on both surfaces of a
solid electrolyte membrane 21, and an electrolyte
membrane/electrode assembly (MEA) is formed in advance. A fixing
plate 8 for fuel cell to fix a fuel cell to a fuel container uses
an electrically insulating material as shown in FIG. 3, wherein a
portion in contact with a fuel cell has a net-like structure, a
porous layer or a slit-like diffusion hole structure 3 through
which air sufficiently diffuses to be fed to a fuel cell, and a
part of surface of the diffusion hole in contact with a fuel cell
has a cathode current collector plate 7 to connect to an anode side
interconnector 4 of an adjacent fuel cell.
[0049] A part of this cathode current collector plate 7 in contact
with a fuel cell has a diffusion hole 3 through which air is
sufficiently fed. In a fuel cell 1, carbon dioxide is formed by an
oxidation of a fuel during power generation, which is discharged to
outside of a fuel container through an air vent hole 15 having a
gas/liquid separation function and being impermeable for liquid
with a cross-sectional structure as shown in FIG. 4A.
[0050] An air vent hole 15 is composed of an air vent tube 51 and a
screw-fastening type of air vent lid 52, having a structure to fix
a water-repellant and porous gas/liquid separation membrane 50 with
an air vent lid. The air vent holes 15 are arranged on a plurality
of surfaces of a fuel container 1 so that at least one hole is in a
ventilating state in any position of a fuel cell power generation
equipment as the cross-sectional structure shown in FIG. 4B.
[0051] As shown in FIG. 5, a fuel cell power generation equipment
is assembled by laminating gasket 10, MEA 9, gasket 10 and a porous
diffusion layer 11, which is a woven fabric of carbon fiber finely
dispersed with polytetrafluoroethylene to make diffusions of air
and water formed easy, on a fuel cell mounting part of a fuel
container in this order, and fixing a fuel cell fixing plate having
mounting holes 19 for air vent holes to a fuel container 1 by an
adhesion or a screw-fastening method. During this fixation process,
a cathode current collector plate is electrically connected to an
anode side interconnector of an adjacent fuel cell, and a start and
an end parts are taken out as output terminals 16.
[0052] In an operation of a fuel cell power generation equipment, a
lid of an air vent hole 15 shown in FIG. 4B, which also has a role
of a fuel feed hole, is removed, through which a liquid fuel such
as an aqueous methanol solution is filled up. Thus filled aqueous
methanol solution is stably fed to an anode of a unit cell mounted
on a bottom surface of the container by penetration, whereas it is
also stably fed to an anode of a unit cell mounted on a upper
surface by sucking up with a sucking material.
[0053] Since a cathode of each unit cell is in contact with ambient
air through a net-like, a porous or a slit-like through hole, a
cathode current collector plate and a cathode diffusion layer,
oxygen in air is fed by diffusion and water formed during power
generation are discharged by diffusion.
[0054] FIG. 6 shows an appearance of a fuel cell power generation
equipment of the present invention. The equipment has a structure
in which a fuel container 1 having air vent holes 15 functions as a
structural body of power generation equipment and also has a
plurality of unit cells 13 fixed on its wall surface with a fuel
cell fixing plate 8, and both ends, electrically connected in
series, are taken out as output terminals 16.
[0055] In power generation, carbon dioxide is formed by oxidizing a
fuel in an anode side, that is, in a fuel container, and discharged
to outside of a fuel container through air vent holes having a
gas/liquid separation function and being impermeable for liquid.
These air vent holes have a feature to ensure a stable operation of
power generation by arranging a plurality of holes on a wall
surface of a fuel container so that at least one vent hole is kept
unsealed from a liquid fuel in any position of the container during
power generation.
[0056] A fuel cell power generation equipment in accordance with
the present invention does not require any facility to compulsorily
feed a fuel or an oxidizing agent gas, and has a structure with
only one layer of unit cell mounted on a wall surface of a
container without adopting a laminated structure of multiple layers
of cells with a separator in between, and further dose not need a
compulsory cooling mechanism due to a sufficient heat radiation.
Therefore, a structure with no power loss coming from auxiliary
equipment, no need of a conductive separator for lamination and
reduced number of parts can be obtained.
[0057] In a fuel cell using an aqueous methanol solution as a fuel,
power is generated by directly converting a chemical energy
possessed by methanol to an electrical energy according to the
following electrochemical reactions.
[0058] In an anode electrode side, an aqueous methanol solution fed
dissociates into carbon dioxide, hydrogen ions and electrons
according to the formula (1).
CH.sub.3OH+H.sub.2O.fwdarw.CO.sub.2+6H.sup.++6e.sup.31 (1)
[0059] Hydrogen ions formed move from an anode to a cathode side in
an electrolyte membrane, and reacts with oxygen gas coming by a
diffusion from air and electrons in accordance with the formula (2)
forming water on an electrode.
6H.sup.++3/2O.sub.2+6e.sup.-.fwdarw.3H.sub.2O (2)
[0060] Therefore, a total chemical reaction accompanied with power
generation is an oxidation of methanol by oxygen to form carbon
dioxide and water, formally the same as in a flaming combustion of
methanol as shown in the formula (3).
CH.sub.3OH+3/2O.sub.2.fwdarw.CO.sub.2+3H.sub.2O (3)
[0061] An opening circuit voltage of a unit cell is about 1.2 V at
around the room temperature. However, the voltage is substantially
0.85 -1.0 V due to an effect of fuel penetration into an
electrolyte membrane. A current density under load is selected so
that the voltage in a practical operation under load becomes in the
range of 0.3 -0.6 V, though not specially limited. Therefore, in a
practical application as a power source, a plurality of unit cells
are used connected in series to provide a prescribed voltage in
accordance with a requirement of load equipment.
[0062] An output current density of unit cell varies by effects of
an electrode catalyst, an electrode structure and others. However,
it is designed so that a prescribed current can be obtained by
effectively selecting an area of power generation part of a unit
cell.
[0063] A supporting body composing a fuel cell power generation
equipment in accordance with the present invention is characterized
in a fuel container to receive a liquid fuel, whose cross-sectional
shape may be square, circular or other any shape without any
particular limitation, so long as it has a shape which can mount a
necessary number of unit cells compactly. However, a cylindrical or
a square shape is preferable for a compact mounting of unit cells
in a specified volume, due to a good mounting efficiency and a good
processability in mounting of a power generation part of fuel
cell.
[0064] There is no specific limitation in a material for supporting
body so long as it is electrochemically inactive in a servicing
environment and has a durability, a corrosion resistance and a
sufficient strength with a thin structure. A material for
supporting body includes, for example, polyethylene, polypropylene,
poly(ethylene terephthalate), poly(vinyl chloride), polyacrylic
resins and other engineering resins, electrically insulating
materials thereof reinforced with various fillers, carbon materials
or stainless steels superior in corrosion resistance in a cell
servicing environment, or ordinary iron, nickel, copper, aluminum
or alloys thereof whose surfaces are treated to make corrosion
resistant and electrically insulating. In any case, there is no
limitation so long as it has strength to support a shape, corrosion
resistance and electrochemical inactivity.
[0065] Inner part of a fuel cell supporting body is used as a space
for fuel storage and transport. A sucking material filled in an
inner part of a cylindrical supporting body to stabilize feeding of
a fuel may be any type so long as it has a small contact angle with
a aqueous methanol solution and is electrochemically inactive and
corrosion resistant, and powdery or fibrous material is preferable.
For example, fibers made of glass, alumina, silica-alumina, silica,
non-graphite carbon and cellulose or water absorptive polymer
fibers are materials with a low packing density and a superior
retention for an aqueous methanol solution.
[0066] As an anode catalyst which composes a power generation part,
fine particles of platinum and ruthenium or platinum/ruthenium
alloys dispersed and supported on carbon powder, whereas, as a
cathode catalyst, fine particles of platinum dispersed and
supported on carbon carrier are materials to be easily
manufactured.
[0067] An anode and a cathode catalysts in a fuel cell of the
present invention are not specially limited so long as they are
used in a usual direct methanol fuel cell, and it is preferable to
use a catalyst of the above described noble metal components added
with a third component selected from iron, tin, rare earth elements
and the like, to stabilize or extend a life of electrode
catalyst.
[0068] As an electrolyte membrane, a hydrogen ion conductive
membrane is used although not limited. Typical material includes
sulfonated or alkylenesulfonated fluoropolymers such as
perfluorocarbon type sulfonic acid resin, poly(perfluorostyrene)
type sulfonic acid resin, polystyrenes; polysulfones;
polyethersulfones; polyetherethersulfones; polyetheretherketones;
and other sulfonated hydrocarbon polymers.
[0069] Materials with a small methanol permeation among these
electrolyte membranes are preferable because they can raise a
coefficient of utilization of fuel with little lowering of cell
voltage by fuel crossover, and generally enable to operate a fuel
cell at the temperature not higher than 90.degree. C. Fuel cell
which can be operated at further higher temperature range can also
be obtained by using a composite electrolyte membrane prepared by a
heat resistant resin micro-dispersed with a hydrogen ion conductive
inorganic material such as hydrates of tungsten oxide, zirconium
oxide and tin oxide; tungstosilicic acid; molybdosilicic acid;
tungstophosphoric acid and molybdophosphoric acid.
[0070] In any of these cases, higher levels of miniaturization and
longer power generation time, which are the effects of the present
invention, are attained by using an electrolyte membrane having a
high hydrogen ion conductivity and a low methanol permeability, due
to a higher coefficient of utilization of fuel.
[0071] The above described hydrated type of acidic electrolyte
membranes may, in general, have problems such as a membrane
deformation induced by a difference in swelling between dry and wet
conditions and an insufficient mechanical strength with a membrane
having a sufficiently high ion conductivity. In these cases, it is
effective methods for enhancing a reliability of cell performance
to use a fiber with superior mechanical strength, durability and
heat resistance as a core material in a form of non-woven fabric or
woven fabric or to add these fibers as reinforcing fillers in
manufacturing an electrolyte membrane.
[0072] In addition, a membrane of polybenzimidazoles doped with
sulfuric acid, phoshoric acid, sulfonic acids or phosphonic acids
may also be used to reduce a fuel permeability of an electrolyte
membrane.
[0073] As another example instead of the above described method, a
power generation part of unit cell can be prepared, for example, by
the following processes. That is, a unit cell is prepared through
the following processes:
[0074] (i) A process to coat a conductive interconnector on an
electrically insulating outer circumferential surface of a liquid
fuel container and make a wall surface of an anode junction part
porous by through holes;
[0075] (ii) A process to prepare a past by adding and dispersing a
solution which is prepared by dissolving an anode catalyst and an
electrolyte resin in a volatile organic solvent in advance, then
form an electrode by coating the past on a notched porous part of a
liquid fuel container in a certain thickness of 10-50 .mu.m;
[0076] (iii) A process to mask the coated anode part, coat a gasket
for sealing on the notched part, then join to a fuel container.
[0077] (iv) A process subsequently to coat an electrolyte solution,
prepared by dissolving in a volatile organic solvent in advance, on
the notched part in contact with an anode electrode so that a
thickness after forming a membrane becomes 20 -50 .mu.m;
[0078] (v) A process then to prepare a past as a binder by mixing a
solution which is prepared by dissolving a. cathode catalyst and an
electrolyte resin in a volatile organic solvent in advance, and
form an electrode by coating the past on an electrolyte membrane in
a certain thickness of 10 -50 .mu.m;
[0079] (vi) A process further to prepare a past by mixing carbon
powder and a prescribed amount of water repellent dispersing agent,
for example, aqueous. dispersion of fine particles of
polytetrafluor
[0080] In the process (iv) among these processes, it is important
to seal the electrolyte membrane part by closely contacting or
adhering using an adhesive with the gasket by making an electrolyte
membrane part larger than a cathode area.
[0081] A cathode current collector is prepared by mounting a
conductive porous material or a net in a cathode side diffusion
layer part of thus obtained unit cell, which is electrically
connected to an interconnector from an adjacent unit cell, and
terminals are taken out from both ends connected in series. It is
an effective method for preventing flooding of water formed during
a fuel cell operation, to provide a diffusion layer in a cathode
side.
[0082] In addition, in manufacturing a diffusion layer, in a case
when a water repellent aqueous dispersing agent contains a
surfactant which is a poisonous component for platinum catalyst or
platinum/ruthenium alloy catalyst, it is an effective method to
coat a past prepared by mixing carbon powder and a certain amount
of water repellent dispersing agent, for example, aqueous
dispersion of fine particles of polytetrafluoroethylene on one side
of a conductive woven fabric such as a carbon fiber, then mount the
fabric so that the coated side is in contact with a cathode after
burning at a decomposition temperature of the surfactant in
advance, and use the woven fabric of carbon fiber as a cathode
current collector.
[0083] In any case, there is no special limitation in a
manufacturing method so long as a unit cell is manufactured by
providing an anode, an electrolyte membrane, a cathode and a
diffusion layer in layers in this order, and forming sufficient
reaction interfaces between anode/electrolyte membrane and
cathode/electrolyte membrane.
[0084] Further, a cell composition without requiring a diffusion
layer may be prepared by coating a past prepared by adding a
prescribed amount of a water repellent dispersing agent, for
example, fine particles of polytetrafluoroethylene to a solution
prepared by dissolving cathode catalyst, electrolyte membrane and
electrolyte in a volatile organic solvent in advance in forming a
cathode.
[0085] A high voltage intended by the present invention can be
attained by using a liquid-fuel container as a platform, preparing
multiple unit cells composed of an anode, an electrolyte membrane
and a cathode on its outer circumferential surface, and connecting
each unit cell in series with a conductive interconnector. In
addition, a compact power source can also be attained, which can be
operated without using auxiliary equipment to compulsorily feed a
fuel and an oxidizing agent or without using auxiliary equipment to
compulsorily cool a fuel cell, and provide a long time continuous
power generation by using a aqueous methanol solution having a high
volume energy density as a liquid fuel.
[0086] This compact power source can be used as a built-in driving
unit for a cellular phone, notebook-type personal computer or a
mobile video camera, and can be continuously used for a long time
by sequentially feeding a fuel prepared in advance.
[0087] Further, it is also effective to use this compact power
source as a battery charger, by connecting it with a charger of,
for example, a secondary battery driven cellular phone,
notebook-type personal computer or mobile video camera, and by
mounting it in a part of container case thereof, to remarkably
reduce a frequency of fuel feeding compared with the above
described case. In this case, the portable electronic device is
driven with a secondary battery by removing the fuel cell power
generation equipment from a container case when in service, whereas
when not in service, the fuel cell power generation equipment is
put in the case and the compact fuel cell power generation
equipment built in the case is connected via a charger to charge
the secondary. Thus, volume of a fuel tank can be enlarged and a
frequency of fuel feeding can be remarkably reduced.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0088] The present invention will be described based on the
Examples hereinbelow.
Comparative Example 1
[0089] FIG. 7 is a cross-sectional drawing showing a separator
structure based on a conventional structure. FIG. 7A shows an
in-plane structure and a longitudinal cross-sectional drawing of
one part and FIG. 7B shows an in-plane structure and a lateral
cross-sectional drawing of the other part, FIG. 8 and FIG. 9 show a
laminated composition of cell and a composition of cell holder,
respectively, FIG. 10A shows a-structure of power source system
composed of 2 sets of laminated unit cells 18 in series and a fuel
container attached, and FIG. 10B shows a cross-sectional structure
of connection between a fuel cell at a lamination end and a fuel
container.
[0090] A graphitized carbon plate of 16 mm width.times.33 mm
length.times.2.5 mm thickness was used for a separator 81. An inner
manifold 82 of 10 mm width.times.4 mm length is mounted at a bottom
of the separator 81, and a fuel feeding channel was provided to
connect a manifold 82 and upper surface of a separator 81 by
forming a rib part 54 by making channels of 1 mm width.times.0.8 mm
depth.times.23 mm length at 1 mm interval as shown by numeral 84 in
FIG. 7B of a lateral cross-sectional drawing of a separator.
[0091] On the other hand, in other surface of the separator, a
feeding channel for an oxidizing agent to connect a side surface of
a separator 21 was made by forming a rib part 84 composed of
channels of 1 mm width.times.1.4 mm depth.times.16 mm length at 1
mm interval in rectangular direction to the opposite surface, as
shown in FIG. 7B and a longitudinal cross-sectional drawing 83 of a
separator.
[0092] As an anode layer, a porous membrane of about 20 .mu.m
thickness was formed on a polyimide film by screen printing of a
slurry, prepared by mixing catalyst powder of 50% by weight of fine
particles of platinum/ruthenium alloy, in an atomic ratio of
platinum/ruthenium being 1/1, dispersed and supported on carbon
carrier, 30% by weight of perfluorocarbon sulfonic acid electrolyte
(trade name: Nafion 117 from DuPont Inc.) as a binder, and
water/alcohol mixed solvent (water:isopropanol:n-propanol is
20:40:40, ratio by weight).
[0093] As a cathode layer, a porous membrane of about 25 .mu.m
thickness was formed on polyimide film by screen printing of a
slurry, prepared by mixing 30% by weight of fine powder catalyst of
platinum supported on carbon carrier and an electrolyte in a
water/alcohol mixed solvent as a binder.
[0094] Thus prepared anode and cathode porous membranes were cut
out each in 10 mm width.times.20 mm length to obtain an anode and a
cathode layers.
[0095] Next, manifold opening part 86 was made in Nafion 117 with
16 mm width.times.33 mm length.times.50 .mu.m thickness, as an
electrolyte membrane.
[0096] An anode layer surface was joined to a power generation part
of the above electrolyte membrane, after being penetrated with
about 0.5 ml of a 5% by weight aqueous alcohol solution of Nafion
117 (a mixed solvent of water:isopropanol:n-propanol is 20:40:40,
ratio by weight, from Fluka Chemika Ltd.), followed by drying at
80.degree. C. for 3 hours under about 1 kg of load. Then, a cathode
layer surface was joined to the electrolyte membrane so that the
electrolyte membrane was overlapped with the above joined anode
layer, after being penetrated with about 0.5 ml of a 5% by weight
of the above described aqueous alcohol solution of Nafion 117,
followed by drying at 80.degree. C. for 3 hours under about 1 kg of
load to prepare MEA 9.
[0097] Next, a poly(ethylene terephthalate) liner 92 with 250 .mu.m
thickness and a neoprene gasket 10 with 400 .mu.m thickness were
prepared by making manifold opening part 86 and power generation
opening part 85 of the same size as in the separator 81.
[0098] Then, a carbon sheet was formed by adding an aqueous
dispersion of water repellent fine particles of
polytetrafluoroethylene (Teflon dispersion D-1 from Daikin
Industries Ltd.) to carbon powder so that a concentration of the
water repellant became 40% by weight after firing, and mixing to a
paste, coating the paste on one surface of a carbon fiber woven
fabric having about 350 .mu.m thickness and a porosity of 87% in a
thickness of about 20 .mu.m, drying at room temperature and firing
at 270.degree. C. for 3 hours. Thus obtained sheet was cut out to
the same size and shape as of the above described MEA electrode to
prepare a diffusion layer 11.
[0099] Then, a fuel sucking material 5 made of pulp paper,
consisting of a channel insertion part 88 in a fuel electrode side
of separator 81 and a manifold insertion part 87, was prepared.
[0100] These parts were laminated, as shown in FIG. 8, in the order
of a separator 81, a sucking material 5, a liner 92, a gasket 10,
MEA 9, a diffusion layer 11, a liner 92 and a separator 81 as one
unit, and 14 units were piled up, followed by pressing at about 5
kg/cm.sup.2 to obtain a laminated cell 94. Said laminated cell 94
was fixed as shown in FIG. 10A, with a fastening band 17 made of
fluorocarbon rubber (Viton from DuPont Inc.), using a SUS 316
holder 105, having a structure shown in FIG. 9, whose surface was
insulated with an epoxy resin (Flep from Toray Thiokol Co.,
Ltd.).
[0101] A fuel container 1 was prepared with polypropylene having
outer dimensions of 33 mm height.times.85 mm length.times.65 mm
width.times.2 mm side wall thickness and having a laminated cell
mounting part 103.
[0102] As shown in FIG. 10B, in a center part of fuel container 1,
an air vent tube 51 with a screw lid 52 having a gas permselective
function which mounted a porous polytetrafluoroethylene membrane,
having a structure similar to that shown in FIG. 4A as a gas/liquid
separation membrane 50, was provided as an air vent hole 15, and
inside of the fuel container is filled with an aqueous methanol
solution 12 as a fuel. Thus prepared two laminated cells having a
structure as shown in FIG. 10B were connected to a fuel cell
mounting part 103 to obtain a power source having a structure as
shown in FIG. 10A.
[0103] The above power source has a size of about 33 mm
height.times.120 mm length.times.65 mm width, and is equipped with
a fuel container having a surface area of power generation part of
about 2 cm.sup.2 and a volume of about 150 ml. The power source
showed a voltage of 5.7 V at the operation temperature of
50.degree. C. and the load current of 0.2 A, and also showed a
voltage of 11.8 V when operated with blasting with a fan to whole
surface of openings in a side wall of power source composed of side
channels in an air-electrode side of separator. This is considered
to happen because oxygen is not fed sufficiently by air diffusion
using a side channel structure with air electrode of a separator
when a power source is loaded. A volume output density of this
power source was about 4.4 W/l without using an air vent fan and
about 9.2 W/l using the air vent fan.
[0104] When a fuel container was filled with 150 ml of a 10% by
weight of aqueous methanol solution, and the power source was
operated at the operation temperature of 50.degree. C. and the load
current of 0.2 A with a blasting fun, an output voltage continued
to show 11.8V for about 4.5 hours, then rapidly dropped. Therefore,
a volume energy density in an operation when the fuel of a 10% by
weight of aqueous methanol solution was filled was 41 Wh/l using an
air vent fan.
[0105] This fuel cell power generation equipment has a structure in
which a liquid fuel is sucked up from a manifold in the bottom of
laminated cell and carbon dioxide formed by an oxidation of a fuel
is discharged from the top of laminated cell. Therefore, it has a
problem that power generation can no longer be continued when it is
placed upside down or turns sideways during operation.
EXAMPLE 1
[0106] FIG. 11 shows a structure of MEA in accordance with this
Example. MEA is formed by joining an anode layer 22 and a cathode
layer 23 using an electrolyte resin as a binder so that they are
overlapped with both sides of an electrolyte membrane 21.
[0107] As an anode layer, a porous membrane of about 20 .mu.m
thickness was formed by screen printing of a slurry, prepared by
50% by weight of fine powder catalyst of platinum/ruthenium alloy
with an atomic ratio of platinum/ruthenium being 1/1, dispersed and
supported on carbon carrier, and 30% by weight of perfluorocarbone
sulfonic acid electrolyte (Nafion 117) in a water/alcohol mixed
solvent (water:isopropanol:n-propanol is 20:40:40 ratio by weight)
as a binder.
[0108] As a cathode layer, a porous membrane of about 25 .mu.m
thickness was formed by screen printing of a slurry, prepared by
30% by weight of fine powder catalyst of platinum supported on
carbon carrier and an electrolyte in a water/alcohol mixed solvent
as a binder.
[0109] The above-mentioned anode and cathode porous membranes were
cut out each in 10 mm width.times.20 mm length to obtain an anode
layer of the electrolyte membrane, after being penetrated with
about 0.5 ml of a 5% by weight aqueous alcohol solution of Nafion
117 (a mixed solvent of water:isopropanol:n-propanol is 20:40:40
ratio by weight, from Fluka Chemika Ltd.), followed by drying at
80.degree. C. for 3 hours for 3 hours under the load of about 1 kg
to prepare MEA.
[0110] Subsequently, a carbon sheet was prepared by adding an
aqueous dispersion of water repellent fine particles of
polytetrafluoroethylene (Teflon dispersion D-1 from Daikin
Industries Ltd.) so that a concentration of the repellant became
40% by weight after firing to carbon powder and mixing to a paste,
coating the paste on one surface of a carbon fiber woven fabric
having the thickness of about 350 .mu.m and the porosity of 87%, to
the thickness of about 20 .mu.m, drying at room temperature and
firing at 270.degree. C. for 3 hours. Thus obtained sheet was cut
out to the same size and shape as of the above described MEA
electrode to prepare a diffusion layer.
[0111] Next, a method for mounting a fuel cell composed of MEA on
an outer circumferential surface of fuel container will be
explained using FIG. 13 showing a cross-sectional structure of a
fuel cell power generation equipment.
[0112] A fuel sucking material 5 made of a glass fiber mat with the
thickness of 5 mm and the porosity of about 85% was mounted on an
inner wall surface of a fuel container 1, made of rigid poly(vinyl
chloride) having the outer dimensions of 65 mm width.times.135 mm
length.times.25 mm height and the wall thickness of 2 mm.
[0113] Eighteen fuel cell mounting parts 2, having the dimensions
of 21 mm width.times.31 mm length.times.0.5 mm depth, were equipped
in each of a top and a bottom of outer wall surface of a fuel
container 1. A diffusion hole 3 was made by preparing slits os 1 mm
width.times.10 mm length in an internal of 1 mm in each fuel cell
mounting part 2 in contact with an anode. In these slits, a carbon
fiber mat with the porosity of 85% was filled so as to contact with
a fuel sucking material 5 mounted at inner wall surface of a fuel
container.
[0114] In an outer surface of the slit, an electroless nickel
plated layer with the thickness of about 50 .mu.m was provided as
an interconnecter 4 to electrically connect to a cathode current
collector 7 of an adjacent fuel cell. Air vent holes 15, having a
gas/liquid separation function with the same structure as shown in
FIG. 4A, were provided at four corners of a top and a bottom of the
fuel container thus obtained.
[0115] Then, a fuel cell fixing plate 8 is made using rigid
poly(vinyl chloride) with the thickness of 2.0 mm, the same as a
fuel container 1, and a slit of 1.0 mm width.times.20 mm length was
provided on its surface in contact with a cathode of each fuel cell
in a rectangular direction to the slit provided in a fuel cell
mounting part 2 as a diffusion hole3. On this fuel cell fixing
plate 8, a cathode current collector 7 made of nickel with a slit,
which was formed in the same shape as its slit part so as to
connect to an interconnector 4 of an adjacent fuel cell, was
fixed.
[0116] In mounting the above described MEA 9 on this fuel
container, each cell was fixed to a fuel container with a fuel cell
fixing plate 8, after arranging MEA 9, having seal gaskets 10 on
both surfaces, in a fuel cell mounting part 2, and a diffusion
layer 11 in its cathode side. In this fixation process, a cathode
current collector 7, which was arranged in advance in a cathode
side surface of the fuel cell fixing plate 8, electrically connects
a cathode and an interconnector 4 from an anode of adjacent fuel
cell, and connects each cell in series. End parts, connecting each
fuel cell, are taken out as cell terminals 16 from an interface of
the fuel cell fixing plate 8 and the fuel container to an outside
of the container. FIG. 12 shows an appearance of a fuel cell power
generation equipment in accordance with this Example.
[0117] On an upper and a bottom surfaces of fuel container 1 having
air vent holes 15, 36 unit cells 13 are mounted by the fuel cell
fixing plate 8, and an output terminal 16 is provided. A 10% by
weight of aqueous methanol solution 12 is charged into the
container through one of the air vent holes 15 of the fuel
container thus mounted with fuel cells. This fuel cell has the
dimensions of about 65 mm width.times.135 mm length.times.29 mm
height and the fuel containing volume of about 150 ml. A power
generation equipment has the power generation surface area of 2
cm.sup.2 and is composed of 36 series.
[0118] An output voltage of this fuel cell power generation
equipment in operation was 12.2 V at the temperature of 50.degree.
C. and the load current of 200 mA. A continuous power generation
was possible for about 4.5 hours in the operation by filling a 10%
by weight of aqueous methanol solution and at the load current of
200 mA. An output density of this fuel cell power generation
equipment was about 9.6 W/l and a volume energy density per litter
fuel was about 50 Wh/l.
[0119] In addition, no change in an output voltage or no pressure
rise in a fuel container was observed even if the power generation
equipment was operated in the positions of upside down or turning
sideways.
[0120] As described above, a high voltage type compact fuel cell of
12 volt class can be attained without laminating with a separator
in between by mounting multiple fuel cells on an outer wall surface
of a liquid fuel container and connecting in series by an
interconnector. In this case, a power source without requiring
auxiliary equipment such as a fuel feed pump and a fan for cathode
gas became possible by contacting an anode and an inner part of
container using a liquid fuel sucking material in the anode side
and exposing a cathode to ambient air through a diffusion
layer.
[0121] In particular, by arranging air vent holes having a
gas/liquid separation function on a plurality of surfaces of a fuel
container, a normal power generation became possible at any
position of a fuel cell, and essential characteristics for a
portable power generation equipment could be attained.
Comparative Example 2
[0122] A compact fuel cell of low voltage type using a separator
will be explained using FIG. 14. Using the same materials and sizes
as in Comparative Example 1 for separator, sucking material, liner,
gasket, MEA and diffusion layer as components of a cell, a
laminated cell 23 was prepared by the same procedure as in
Comparative Example 1 so as to have four unit cells. This laminated
cell was inserted to a cell holder 105, and fastened with a
fastening band 17 made of fluorocarbon rubber in the same manner as
in Comparative Example 1.
[0123] A fuel cell was made of polypropylene with the outer
dimensions of 33 mm height.times.16 mm length.times.65 mm width and
the wall thickness of 2 mm.
[0124] As shown in FIG. 14, air vent holes 15 mounted with porous
polytetrafluoroethylene membranes having the same structure as
shown in FIG. 4A were provided at the central part of an upper
surface of a fuel container 1.
[0125] A power source was prepared using thus prepared laminated
cell 23 combined with a fuel container 1 with the same composition
as in Comparative Example 1. Thus obtained power source has the
dimensions of about 33 mm height.times.82 mm length.times.16 mm
width, with the surface area of power generation part of about 2
cm.sup.2 and a fuel container 1 having the volume of about 20
ml.
[0126] The power source shows 0.58 V at the operation temperature
of 50.degree. C. and the current load of 0.2 A, and 1.26 V when
operated by blasting with a fan to the whole area of opening part
in a side wall of the power source composed of side channels in an
air electrode side of a seperator. It is considered to happen
because oxygen was not fed by air diffusion with the air electrode
side channel structure of a seperator under a loaded power source.
A volume output density of this power source was about 2.7 W/l when
an air vent fan was not used and about 5.8 W/l when the air vent
fan was used.
[0127] An output voltage was 1.26 V in the operation by filling 20
ml of a 10% by weight of aqueous methanol solution, using a blast
fan at the operation temperature of 50.degree. C. and the load
current of 0.2 A. The voltage continued for about 5 hours, then
rapidly dropped. Therefore, a volume energy density per litter fuel
of a 10% by weight of aqueous methanol solution was 29 Wh/l when a
blast fan was used.
[0128] This fuel cell power generation equipment has a structure in
which a liquid fuel is sucked up from a manifold in the bottom of
laminated cell and carbon dioxide formed by an oxidation of a fuel
is discharged from the top of laminated cell. Therefore, it has a
problem that power generation can no longer be continued when it is
placed upside down or turns sideways during operation.
EXAMPLE 2
[0129] FIG. 15 shows a cross-sectional structure of a rectangular
type and low voltage type of power generation equipment using
methanol as a fuel in accordance with this Example, and FIG. 16
shows outline of a mounting method for fuel cells. MEA was prepared
by an almost similar method as in Example 1. A porous membrane of
about 20 .mu.m thickness was formed on a polyimide film with the
dimensions of 30 mm width.times.50 mm length by screen printing
using a slurry, which was prepared by mixing a catalyst powder of
50% by weight of platinum/ruthenium alloy fine particles, an atomic
ratio of platinum/ruthenium being 1/1, dispersed and supported on
carbon carrier, 30% by weight of perfluorocarbon sulfonic acid
electrolyte (Nafion 117) as a binder and a water/alcohol mixed
solvent (water:isopropanol:n-propanol was 20:40:40, ratio by
weight), followed by drying at 90.degree. C. for 3 hours to get an
anode porous layer.
[0130] A porous cathode layer of about 25 .mu.m thickness was
formed on a polyimide film with the dimensions of 30 mm
width.times.50 catalyst powder of 30% by weight of fine platinum
powder supported on carbon carrier, an electrolyte as a binder and
a water/alcohol mixed solvent, followed by drying at 90.degree. C.
for 3 hours.
[0131] Thus prepared anode and cathode porous membranes were cut
out each in 10.times.10mm size to obtain an anode layer and a
cathode layer. Sulfonated polyetherethersulfone membrane of 28 mm
width.times.56 mm length.times.50 .mu.m thickness having 790 g/eq
was used as an electrolyte.
[0132] Firstly, eight anode layers were penetrated with about 0.5
ml of a 5% by weight aqueous alcohol solution of Nafion 117 (from
Fluka Chemika Ltd.) in each surface, then arranged evenly on one
surface of an electrolyte membrane, followed by drying of each
electrode at 80.degree. C. for 3 hours under the load of about 1
kg.
[0133] Then, a cathode layer surface was penetrated with about 0.5
ml of a 5% by weight aqueous alcohol solution of Nafion 117, then
arranged on the opposite side surface of the above electrolyte
membrane joined with an anode so as to be overlapped with the anode
layer, followed by drying at 80load of about 1 kg on each cell to
prepare MEA.
[0134] As shown in FIG. 16, a fuel container 1 was made of rigid
poly(vinyl chloride), having the outer dimensions of 22 mm
width.times.79 mm length.times.23 mm height and wall thickness of 2
mm. As shown in FIG. 15 of a cross-sectional structure, four fuel
cell mounting parts 2, having the dimensions of
[0135] In an outer surface of this mounting parts 2, a nickel layer
with the thickness of about 0.1 mm was formed by an electroless
plating method as an interconnector 4 in order to electrically
connect to an adjacent fuel cell. A fuel sucking material 5 was
provided by adhering a glass fiber mat with the thickness of 1 mm
thickness and the porosity of about 70% on an inner wall of the
fuel container 1, and further a low density fuel retaining layer 18
filled with a glass fiber was provided in the container so as to
make a porosity about 85%. Eight air vent holes 15, with a
structure as shown in FIG. 4A and an inner diameter of 2 mm, were
provided at corners of an upper and a bottom surfaces of the fuel
container 1.
[0136] As shown in FIG. 16, a fuel cell fixing plate 8 as a holding
plate for a fuel cell was prepared using rigid poly(vinyl chloride)
with the dimensions of 22 mm width.times.79 mm length.times.1 mm
thickness, and a slit of 1 mm width.times.10 mm length was provided
in its surface in contact with a cathode of each fuel cell in a
rectangular direction to the slit of a fuel cell mounting part 2 of
fuel container 1, and also air vent hole mounting holes 19 were
provided at the four corners.
[0137] A cathode current collector 7 made of nickel with the
thickness of 0.2 mm having a slit was mounted on a fuel cell fixing
plate 8 to connect to an interconnector in an anode side of an
adjacent fuel cell.
[0138] The fuel cell of this Example was prepared by laminating an
anode side gasket made of neoprene rubber, MEA 9, a cathode side
diffusion plate 11, a cathode side gasket 10 made of neoprene
rubber and a fuel cell fixing plate 8 in this order as shown in
FIG. 16, and said fixing plate was fixed to a fuel container 1 by
screwing its peripheral part.
[0139] Output terminals 16 were made by connecting an anode side
terminal 6 and a cathode side terminal 6 mounted in an upper and a
bottom sides of the fuel container 1 each in parallel. Thus
obtained fuel cell power generation equipment has the outer
dimension of 22 mm width.times.79 mm length.times.27 mm height and
the power generation area of 1 cm.sup.2 , and composed of four
series.times.two parallel fuel cells.
[0140] A volume of the fuel container 1 was about 20 ml. After
filling a 10% by weight of aqueous methanol solution in the fuel
container through an air vent hole 15, the fuel cell was operated
at the operation temperature of 50.degree. C. and the load current
of 200 mA to give an output voltage of 1.3 V. A continuous power
generation was also carried out after filling with 20 ml of a 10%
aqueous methanol solution at the load current of 200 mA to give a
stable voltage for about 5 hours with an output voltage of 1.3 V.
An output density of this cell was about 5.5 W/l and a volume
energy density per litter fuel was about 28 Wh/l.
[0141] During the operation, no change in an output voltage or no
pressure rise in a fuel container was observed even if the power
generation equipment was operated in the positions of upside down
or turning sideways.
[0142] Thus, a compact fuel cell of 1.3 volt class could be
attained by mounting multiple fuel cells on one outer wall surface
of a liquid fuel container, connecting in series with an
interconnecter, and connecting the series cell groups mounted on
multiple surfaces in parallel, without laminating with a separator
in between. In this case, a power source was obtained without
requiring any auxiliary equipment such as a fuel feed pump or a fan
for cathode gas, by contacting an inner part of the container and
an anode with a liquid fuel sucking material in an anode side and
exposing a cathode to ambient air through a diffusion layer.
[0143] Further, shaking of the liquid fuel during operation could
be reduced by filling inside of a fuel container with a low density
fuel sucking material. In particular, by arranging air vent holes
having a gas/liquid separation function on a plurality of surfaces
of a fuel container, a normal power generation became possible at
any position of a fuel cell, and essential characteristics for a
portable power generation equipment could be attained.
EXAMPLE 3
[0144] In this Example, a fuel cell with a metal fuel container
coated with epoxy resin as a platform will be described.
[0145] MEA and a cathode side diffusion layer were prepared in the
same way as in Example 2A. A fuel container made of SUS 304 was
prepared with the outer dimensions of 22 mm width.times.79 mm
length.times.23 mm height and the thickness of 0.3 mm, as shown in
FIG. 17. The container is composed of a frame and an upper and a
bottom lids having 4 faces of press formed fuel cell mounting parts
2 with the dimensions of 16 mm width.times.16 mm length.times.0.5
mm depth.
[0146] A slit of 0.5 mm width.times.10 mm length was provided by
punching as a diffusion hole 3 in a part having the size of 10 mm
width.times.10 mm length in the center of a fuel cell mounting part
2. Air vent holes 15 with an inner diameter of 1 mm made of SUS 304
were mounted without using a gas/liquid separation membrane in
corner parts of an upper and a bottom lids. Using these parts, a
fuel container 1 was prepared by weld-sealing, after filling the
container with a fuel sucking material made of glass fiber mat
having the porosity of about 80%.
[0147] An insulation layer 20 was formed by coating a liquid epoxy
resin coating material (Flep from Toray Thiokol Co. Ltd.) on an
outer surface of fuel container 1 in a thickness of 0.1 mm,
followed by thermal curing. A surface of fuel cell mounting part 2
was electroless plated with nickel as an interconnecter 4 in an
anode side in the same shape as in Example 2.
[0148] A slit of 1 mm width.times.10 mm length was provided using
rigid poly(vinyl chloride) with the dimensions of 22 mm
width.times.79 mm length.times.1 mm thickness in a fuel cell fixing
plate similar to Example 2, in a surface contacting a cathode of
each fuel cell in a rectangular direction to the slit in a fuel
cell mounting part 2, and air vent holes 15 were also provided at
the four corners. Using this slit, a cathode current collector 7
made of nickel with a slit having the thickness of 0.2 mm was
mounted to connect to an interconnecter 4 in an anode side of an
adjacent fuel cell.
[0149] The fuel cell of this Example was obtained, in the same way
as in Example 2, by laminating anode side gasket made of
fluorocarbon rubber, MEA, cathode side gasket made of fluorocarbon
rubber, cathode side diffusion layer and fuel cell fixing plate in
this order, and fixed to a fuel container by fastening a peripheral
part of said fixing plate with a heat shrinkable 100 .mu.m thick
resin tube with a slit. Output terminals were obtained by
connecting, each in series, an anode side terminals and a cathode
side terminals mounted on an upper and a bottom sides of a fuel
container.
[0150] Thus obtained fuel cell power generation equipment had the
outer dimensions of 22 mm width.times.79 mm length.times.27 mm
height and the power generation area of 1 cm.sup.2, and composed of
eight series of fuel cells. A volume of the fuel container was
about 38 ml. After filling a 10% by weight of aqueous methanol
solution as a fuel with a syringe through air vent holes of this
fuel container, the fuel cell power generation equipment was
operated at the operation temperature of 50.degree. C. and the load
current of 100 mA to give an output voltage of 2.6 V.
[0151] In addition, a continuous power generation was carried out
at the load current of 100 mA after filling the fuel container with
about 37 ml of a 10% by weight of aqueous methanol solution, a
stable voltage was obtained at an output of 2.6 V for about 4
hours. An output density of th
[0152] With this fuel cell, no change in an output voltage, no
leakage of the liquid fuel or no pressure rise in a fuel container
was observed even generation equipment was operated in the
positions of upside down or turning sideways.
[0153] Thus, a compact fuel cell of 2.6 volt class could be
attained by mounting multiple fuel cells on one outer wall surface
of a liquid fuel container, connecting in series with an
interconnecter and connecting the series cell groups mounted on
multiple surfaces in parallel, without laminating with a separator
in between. In this case, a power source could be obtained without
requiring any auxiliary equipment such as a fuel feed pump or a fan
for cathode gas, by contacting an inner part of the container and
an anode with a liquid fuel sucking material in an anode side and
exposing a cathode to ambient air through a diffusion layer.
[0154] A fuel container of this Example was characterized in that a
large volume can be obtained because the container is composed of a
metal material with an insulation treated surface. In addition, it
was also possible to prevent a leakage of liquid fuel and to
provide a stable power generation in any position of the container
during power generation by filling an inside of the container with
a relatively low density of fuel sucking material and by providing
only small open holes without having a gas/liquid separation
function. It also became possible in production of said power
generation equipment, to easily fi.times.each fuel cell using a
heat shrinkable resin tube.
EXAMPLE4
[0155] In this Example, a polygonal cylinder type methanol fuel
cell power generation equipment with a metal fuel container coated
with epoxy resin as a platform will be described.
[0156] MEA with the outer dimensions of 24 mm width.times.29 mm
length and the outer dimensions of electrode of 20 mm
width.times.25 mm length was prepared in the same way as in Example
2. A cathode diffusion layer with the shape of 20 mm width.times.25
mm length was also prepared in the same way as in Example 2.
[0157] The fuel cell was a hexagonal cylinder having the dimensions
of 28 mm side.times.190 mm height and the wall thickness of 0.3 mm,
and composed of press formed fuel cell mounting part with the
dimensions of 24 mm width.times.29 mm length.times.0.5 mm depth in
each side and hexagonal upper and bottom lids.
[0158] Slits of 0.5 mm width.times.25 mm length were punched at the
interval of 0.5 mm, in the central part of 20 mm width.times.25 mm
length of a fuel cell mounting part. Six air vent holes having a
gas/liquid separation function and the inner diameter of 2 mm were
provided in peripheral parts of upper and bottom lids, as shown in
FIG. 4. Upper and bottom lids were weld-sealed, after mounting a
glass fiber mat having the thickness of 5 mm and the porosity of
about 85% in an inner wall part of the hexagonal cylinder. An outer
surface of a fuel container was coated with a liquid epoxy resin
coating material (Flep from Toray Thiokol Co., Ltd.) in the
thickness of 0.1 mm, followed by thermal curing and electroless
plating with nickel as an interconnecter in an anode side, in the
same shape as in Example 2.
[0159] Similar to Example 2, a fuel cell fixing plate 8 as a
holding plate for a fuel cell was prepared using rigid poly(vinyl
chloride) with the dimensions of 28 mm width.times.190 mm
length.times.1 mm thickness, and a slit of 0.5 mm width.times.20 mm
length was provided at the interval of 0.5 mm in its surface in
contact with a cathode of each fuel cell in a rectangular direction
to the slit in the notched part of fuel container. Using these
slits, a cathode current collector made of nickel having slits with
the thickness of 0.2 mm was mounted in order to connected to an
interconnector in an anode side of an adjacent fuel cell.
[0160] The fuel cell of this Example was obtained, in the same way
as in Example 2, by laminating anode side gasket made of
fluorocarbon rubber, MEA, cathode side gasket made of fluorocarbon
rubber, cathode side diffusion layer and fuel cell fixing plate in
this order, and fixed to a fuel container by fastening a peripheral
part of a fuel cell fixing plate with a heat shrinkable 100 .mu.m
thick resin tube with a slit. FIG. 18 shows thus obtained fuel cell
power generation equipment.
[0161] On an outer wall of a hexagonal cylinder type fuel container
1 having six air vent holes each in an upper and a bottom parts, 36
unit cells 13 were mounted, which were each connected in series and
output terminal 16 was taken out from the fuel container 1. Thus
obtained fuel cell power generation equipment has hexagonal
cylinder with the outer dimensions of about 28 mm side and about
190 mm height and the power generation area of 5 cm.sup.2 and a
direct current power generating equipment composed of 36 series. A
volume of the fuel container was about 300 ml.
[0162] After filling a 10% by weight of aqueous methanol solution
in a fuel container, a continuous power generation was carried out
at the load current of 500 mA to give a stable voltage for about 4
hours at the output voltage of 12.1 V. An output density at this
condition was about 15 W/l and a volume energy density per litter
fuel was about 60 Wh/l.
[0163] With this fuel cell, no change in an output voltage, no
leakage of the liquid fuel or no pressure rise in a fuel container
was observed even if the power generation equipment was operated in
the positions of upside down or turning sideways.
[0164] Thus, a compact fuel cell of 12 volt class could be attained
by mounting multiple fuel cells on one outer wall surface of a
liquid fuel container, connecting in series with an interconnecter
and connecting the series cell groups mounted on multiple surfaces
in parallel, without laminating with a separator in between. In
this case, a power source could be obtained without requiring any
auxiliary equipment such as a fuel feed pump or a fan for cathode
gas, by contacting an inner part of the container and an anode with
a liquid fuel sucking material in an anode side and exposing a
cathode to ambient air through a diffusion layer.
[0165] This Example is characterized in that an output was improved
by providing a comparatively large power generation area, and it
becomes possible to obtain a stable power generation in any
position of the container during operation. In addition, it also
became possible in production of said power generation equipment,
to easily fix each fuel cell using a heat shrinkable resin
tube.
EXAMPLE5
[0166] A square type high output power generation equipment using a
aqueous methanol solution as a fuel will be described. As an anode
layer, a porous membrane of about 20 .mu.m thickness was formed by
screen printing of a slurry, which was prepared by mixing catalyst
powder of 50% by weight of fine particles of platinum/ruthenium
alloy, in the atomic ratio of platinum/ruthenium being 1/1,
dispersed and supported on carbon carrier, 30% by weight of
perfluorocarbone sulfonic acid electrolyte (Nafion 117) as a binder
and a water/alcohol mixed solvent (water:isopropanol:n-propanol is
20:40:40, ratio by weight).
[0167] As a cathode layer, a porous membrane of about 25 .mu.m
thick was formed with a roll method using a slurry, which was
prepared by mixing catalyst powder of 50% by weight of fine
particles of platinum supported on carbon carrier and an aqueous
dispersion of polytetrafluoroethylene as a binder, so that the
ratio by dry weight became 25% by weight. This cathode layer was
fired in air at 290.degree. C. for one hour to decompose a
surfactant in the aqueous dispersion.
[0168] Thus prepared anode and cathode porous membranes were cut
out each in the size of 16 mm width.times.56 mm length to obtain an
anode and a cathode.
[0169] Then, Nafion 117 electrolyte membrane with the thickness of
50 .mu.m was cut out in the size of 120 mm width.times.180 mm
length, and about 0.5 ml of a 5% by weight aqueous alcohol solution
of Nafion 117 (from Fluka Chemika Ltd.) was penetrated to anode
layer surface, followed by joining and drying at 80.degree. C. for
3 hours under the load of about 1 kg. Then, a surface of cathode
layer was penetrated with a 10% by weight aqueous alcohol solution
of Nafion 117 (from Fluka Chemika Ltd.), so that the solution
became 25% by weight based on dry weight of the cathode, followed
by joining so as to overlap with an anode layer joined in advance,
drying at 80.degree. C. for 3 hours under the load of about 1 kg to
prepare MEA.
[0170] A fuel container had the outer dimensions of 28 mm
width.times.128 mm length.times.24 mm height and was prepared by
adhering rigid poly(vinyl chloride) with the wall thickness of 2 mm
using an adhesives. Similar to Example 2, 18 notches with the
dimensions of 16 mm width.times.56 mm length.times.0.1mm depth were
provided for fuel cell mounting in an outer wall of this hexahedron
container.
[0171] Slits of 0.5 mm width.times.16 mm length were provided at
the interval of 0.5 mm in the central part of 16 mm width.times.56
mm length in a fuel cell mounting part. Eight air vent holes with a
gas/liquid separation function and the inner diameter of 2 mm, the
same as in FIG. 4A, were provided at four corners of two maximum
surfaces of a fuel container.
[0172] An electroless nickel plated metalizing layer with the
thickness of about 50 .mu.m was forme also provided at the interval
of 0.5 mm, in the part of a fuel cell mounting plate contacting to
a cathode in matching size with each outer wall surface of a fuel
container in the same way as in Example 2.
[0173] Further, a cathode current collector with a slit was mounted
on a fuel cell fixing plate. Output terminals connected in series
were taken out from 18 fuel cells mounted on an outer wall surface
of a fuel container by a cathode current collector adjacent to an
interconnector in an anode side.
[0174] Thus obtained parts were laminated in the order of an anode
side gasket and MEA, and peripheral part of each fuel cell in a
fuel cell mounting plate and peripheral part of a fuel container
were joined with an adhesive. Thus obtained fuel cell power
generation equipment was a direct current power generation
equipment having the outer dimensions of about 28 mm
width.times.128 mm length.times.28 mm height as shown in FIG. 19,
mounted with 18 series of unit cells 13 with the power generation
area of about 9 cm.sup.2 on a wall surface of a fuel container 1,
and having output terminals 16 and eight air vent holes 5 with a
gas/liquid separation function, at an upper and a bottom surfaces.
A inside volume of the fuel container was about 59 ml.
[0175] After filling about 55 ml of a 10% by weight of aqueous
methanol solution in the fuel container, a continuous power
generation was carried out at the load current of 1A, to give a
stable voltage for about 45 minutes at an output of 6.1 V.
[0176] With this fuel cell, no change in an output voltage, no
leakage of the liquid fuel or no pressure rise in a fuel container
was observed even if the power generation equipment was operated in
the positions of upside down or turning sideways.
[0177] Thus, a compact fuel cell of 6 volt class could be attained
by mounting multiple fuel cells on one outer wall surface of a
liquid fuel container, connecting in series with an interconnecter
and connecting the series cell groups mounted on multiple surfaces
in parallel, without laminating with a separator in between. In
this case, a power source could be obtained without requiring any
auxiliary equipment such as a fuel feed pump or a fan for cathode
gas, by contacting an inner part of the container and an anode with
a liquid fuel sucking material in an anode side and exposing a
cathode to ambient air through a diffusion layer.
[0178] This example enables a structure with a reduced number of
component parts without lowering performance even if a diffusion
layer is omitted, by giving a water repellency to a cathode
catalyst layer by dispersing polytetrafluoroethylene to make a
diffusion of water formed easy.
[0179] The above description was made with reference to Examples,
however, it is apparent to those skilled in the art that various
changes and modifications may be done in the present invention
within the spirit of the invention and the spirit and scope of the
attached claims.
[0180] The present invention is characterized in that a container
for a liquid fuel is used as a platform, fuel cells are mounted on
its wall surface, and said cells are electrically connected in
series or in a combination of series and parallel.
[0181] Fuel cells are mounted on a fuel container as a platform and
liquid fuel is sucked up and fed to each fuel cell by capillary
force, by filling a liquid fuel holding material in said
container.
[0182] Oxygen (an oxidizing agent) in air is fed through a
diffusion hole in each fuel cell having power generation part in an
outer circumferential surface. By this, a fuel cell having a simple
system without requiring auxiliary equipment for feeding fuel and
an oxidizing agent can be realized.
[0183] By using an aqueous methanol solution having a high volume
energy density as a liquid fuel, a longer time of power generation
per litter fuel can be attained compared with the case using
hydrogen as a fuel, and a continuous power generation equipment
without requiring charging such as conventional secondary battery,
can be obtained by sequential feeding of a fuel.
[0184] Furthermore, by mounting fuel cells on multiple wall
surfaces of a fuel container and providing multiple air vent holes
having a gas/liquid separation function on the wall surfaces, a
power generation equipment providing stable and continuous power
generation in any position of the fuel container can be
attained.
* * * * *