CA2411103A1

CA2411103A1 - Electrically conductive composite plates including flow field for direct methanol air breating micro fuel cell applications

Info

Publication number: CA2411103A1
Application number: CA002411103A
Authority: CA
Inventors: Biswajit Choudhury; Peter Andrin; Jan Ottenhof; Brent E. Elliott; Scott B. Fulton
Original assignee: DuPont Canada Inc
Current assignee: DuPont Canada Inc
Priority date: 2002-11-04
Filing date: 2002-11-04
Publication date: 2004-05-04
Also published as: AU2003275878A1; WO2004042855A2; WO2004042855A3

Abstract

Disclosed are electrically conductive current collector plates for use in liquid feed direct methanol micro fuel cell applications wherein the plates comprise graphite fibers and/or graphite powder and a polymer resin, preferably the polymer is selected from a liquid crystalline polymer, a thermoset and a thermoplastic polymer, and most preferably the polymer is liquid crystalline polymer. Also disclosed are conductive plates for use in liquid feed direct methanol micro fuel cell applications having different flow field designs and optionally including current collecting grooves.

Description

ELECTRICALLY CONDUCTIVE COMPOSITE PLATES INCLUDING
FLOW FIELD FOR DIRECT METHANOL AIR BREATHING MICRO FUEL
CELL APPLICATIONS
Field of the Invention:
[0001] This invention relates to electrically conductive polymer-based composite flow field current collector plates intended for use in liquid feed direct methanol micro fuel cell applications.
Background of the Invention:

[0002) With the increasing popularity of consumer electronics, the demand for long lasting power sources is getting stronger. The demands are in the range of a few hundred milliwatts to one kilowatt and presently different types of rechargeable batteries largely meet these demands. These batteries, however, are expensive, have a relatively short life and have considerable environmental issues with their disposal problems.

[0003) Fuel cells in general are battery replacements and like batteries, they produce electricity through an electrochemical process without combustion and virtually with no environmental emissions. A fuel cell differs from a battery in that it derives its energy from supplied fuel, as opposed to the energy stored in the electrodes of the battery. Because a fuel cell is not tied to a chargeldischarge cycle, it can, in principle maintain a specific power output as long as fuel is continuously supplied to it.

[0004] One of the attractive types of fuel cells is the polymer electrolyte membrane (PEM) fuel cell. A single PEM fuel cell consists of an anode and a cathode compartment separated by a thin, ionically conducting membrane. Hydrogen is typically used as the fuel for producing the electricity and can be processed from methanol, natural gas, and petroleum or stored as pure hydrogen. Direct methanol fuel cells (DMFCs) utilize methanol, in a gaseous or liquid form as fuel, thus eliminating the need for expensive reforming operations to convert methanol to hydrogen. Methanol, as a fuel, has high energy density and is easily obtained, stored and transported. DMFCs provide for a simpler PEM fuel cell system, lower weight, streamlined production and thus lower costs.

[0005] In a standard DMFC, a dilute aqueous solution of methanol is fed as a fuel on the anode side and the cathode side is exposed to forced or ambient air (oxygen). A
Nafion~ type proton conducting membrane typically separates the anode and the cathode sides. Several of these fuel cells can be connected in series or parallel depending on the power requirements.

[0006] Dilute aqueous methanol solution (about 3-4% methanol) is used on the anode side as fuel for DMFC operation. The methanol concentration in the fuel may be critical for obtaining optimum DMFC efficiency. With a higher concentration of methanol, methanol crossover to the cathode side may occur, which reduces the efficiency of the fuel cell. With low methanol concentration, the anode side experiences fuel starvation, also resulting in low cell efficiency. Typically, DMFC
designs are large stacks with forced airflow operating at temperatures of about 60 °C
to 80 °C, requiring various auxiliary components and a rather complicated control system. Such a DMFC does not meet the requirements for the low power battery replacement applications such as use in laptops, cell phones, pagers, etc.;
however, an air breathing DMFC (as opposed to forced airflow) fits the requirements perfectly.
Smaller air breathing DMFC designs require the miniaturization of all system components and their integration in a small unit for portable applications, which increases the complexity of the system. Also, using very dilute aqueous methanol solutions to avoid methanol crossover is not very practical, as it requires carrying around a large quantity of fuel, which is not acceptable for the design of portable applications. Therefore one solution is to have a separate source of methanol and water, and then mixing them in-situ for the fuel cell reaction.

[0007] Even distribution of the methanol fuel onto the anode and efficient removal of by-product water and carbon dioxide from the cathode of the fuel cell is critical for optimum performance. If a specific fuel flow path (called a flow field) is not present, then the fuel flow will follow the path of least resistance in the fuel cell.
This path of least resistance results in uneven distribution of the fuel to the anode. In addition, if an inefficient flow field is present, carbon dioxide by-products can accumulate in areas and prevent fuel from accessing the anode or the electro-catalyst, resulting in significant mass transport loss. In air-breathing systems, this may result in back pressure, which is formed due to the lack of means for exhausting the carbon dioxide out of the fuel cell.

[0008] To aid in supplying the fuel, and more specifically methanol and water solution to the anode, it would be beneficial to form a fuel flow field on the current collector plates that would provide for the even distribution of the fuel onto the anode, and more specifically onto the anode backing and thus into the membrane electrode assembly (MEA). The equal distribution of the fuel would help to provide the optimum performance of the fuel cell device.

[0009] An ideal flow field plate should be a thin, lightweight, low cost, durable, highly conductive, corrosion-resistant structure that provides an effective flow-field configuration. The conventional flow field plates for direct methanol micro fuel cell applications are fabricated of metal wire fabrics or screens, wherein the wires form a series of coils, waves and crimps, or other undulating contour. The collectors are disposed within a gasket frame through which reactants are supplied to (and removed from) the collectors by a series of channels. These channels span the width of the collectors in an effort to evenly distribute reactants and products. Tn terms of efficient distribution of methanol onto the anode side and current collecting property, these metal plates perform very well and give very good beginning-of life (BOL) performance for air breathing direct methanol fuel cell. Unfortunately, these metal flow field plates are prone to oxidative degradation under fuel cell conditions.
Formation of a passive oxidative layer on the plate surface occurs as a result of oxidation, which diminishes the reaction kinetics and hence the performance of the fuel cell over time. Moreover, the oxidative by-product of the metal plates may also contaminate the fuel source, i.e. aqueous methanol solution, which in turn contaminates the MEA. This adversely impacts the MEA performance over time and the fuel cell's effective life is thereby reduced. Therefore, to make an air breathing direct methanol fuel cell product successful, it would be desirable to develop flow field micro fuel cell plates that are stable in direct methanol fuel cell conditions.

[0010] A number of technologies are being considered for developing non-corrosive flow field plates, which act as current collectors in direct methanol micro fuel cells.
Many fuel cell researchers are trying to develop inert metal coatings to help the cost-effective metal plates from such adverse effects. Unfortunately, these coatings are very expensive and increase the total cost of the cell hardware substantially.
Others have considered applying a conductive polymer coating on the metal flow field plates to make them corrosion resistant. This method normally reduces the electrical conductivity of the plate, which in turn reduces the cell performance.
[0011 ] Previous technologies relied mostly upon the modification of the surface properties of the metal flow field plates to make them corrosion resistive and still take advantage of the flow field properties of the plates. Modification of the surface properties of metal flow field plates by conductive polymer coating helped in achieving less corrosive plates hut their conductivity loss resulted in low performance of the cell. The resistive loss of the cells is too high for these coated plates.
Alternatively, inert metal coatings provide the desired corrosion resistance, but they increase the cost of the plate material.
[0012] The following are descriptions of the published patent literature that try to address this problem.
[0013] WO 0241433 A1 published by MTI discloses the use of metal plates with different surface patterns to enhance the compression of the MEA. The surface patterns are designed to assist better fuel distribution on the anode. WO 0241433 A1 also discloses the detailed cell architecture of the proposed direct methanol air breathing micro fuel cell.
[0014] US Patent Application 2002/0076598 A1 published by Motorola discloses the use of metal plates with different surface patterns (flow field designs) in passive direct methanol fuel cell stack. Better conductivity is claimed using metal flow field plates having a surface coating of various inert metals.
[0015] US 5798187, US 6037072 and US 6207310 issued to Los Alamos National Lab disclose various types of flow field patterns constructed on metal plates for direct methanol micro fuel cell applications. Also claimed is the benefit of using metal mesh having different mesh structures for flow field purpose in direct methanol micro fuel cell.
[0016] WO 0045457 published by University of California at Los Angeles (UCLA) discloses the concept of making micro flow field channels on thin metal layers using microelectronics mechanical systems for direct methanol micro fuel cell applications.
[0017] US 6268077 issued to Motorola discloses the concept of button-like MEA and fuel cells for direct methanol micro fuel cell applications.
Also described is the use of metal current collector plates for better conductivity.
[0018] WO 0026980 published by Motorola discloses the concept of planar fuel cells for direct methanol applications. Also described is the use of metal flow field plates confined in plastic frames as current collectors.
[0019] US 5759712 issued to Manhattan Scientific relates to the concept of direct methanol micro fuel cell. There is no teaching regarding the material of construction for the current collectors.
[0020] US 6326097 also issued to Manhattan Scientific disclosed concepts relating to direct methanol micro fuel cell design, including all the components, such as fuel delivery system, fuel cartridge design, cell phone and laptop hardware designs to accommodate these direct methanol micro fuel cells as power source.
[0021 ] None of the patents referenced above teach the use of polymer composite plates for passive direct methanol micro fuel cell system.
[0022] Accordingly, it is one object of one aspect of the present invention to provide simpler and more effective non-metallic and non-corrosive flow field plates for direct methanol air breathing micro fuel cell applications.
[0023] The disclosures of all patents/applications referenced herein are incorporated herein by reference.

[0024) There remains a need, therefore, for providing collector plates made of materials other than metal for use in passive direct methanol micro fuel cell systems.
Summary of the Invention:
[0025) In accordance with different aspects of the present invention, there is provided:
[002b) a. The use of polymer composite material as non-corrosive flow field current collector plate material for air breathing direct methanol micro fuel cell application.
[0027] b. In particular; the polymer composite material comprises graphite fiber and/or graphite powder based polymer composites, and preferably the polymer is a liquid crystalline polymer (LCP).
[0028] c. The use of a rectangular cell geometry, rather than conventional square cell geometry [0029] i. to achieve uniform MEA compression and hence the enhancement of the cell performance.
[0030] ii. To allow the use of less flexible plates and hence much thinner plates in the cell; and [0031 ] iii. To possibly use serial arrangement of planar cells to increase the power output.
[0032) d. Provide conductive plates combined with flow fields and current collecting grooves, such as, [0033) i. Perforated flat and ribbed structure with ridges and grooves to provide uniform delivery of methanol on anode and removal of carbon dioxide by-product. The dimension of the holes and the grooves depend on the particular applications and can preferably vary from 20 thou (thousandths of an inch) to 100 thou, more preferably from 30 thou to 60 thou depending on the application.
[0034] ii. Recessed flow field surface to provide uniform compression of MEA in the absence of gaskets. The depth of the recessed surface could preferably vary from 20 thou to 80 thou depending on the cell and MEA dimensions.
[0035] iii. Different aspect ratios for different plate dimensions. The number of holes in a particular piece can be varied depending on the application. They can preferably vary from 20% to 75%, more preferably 40% to 60%, depending on fuel concentration, cell dimension, operating conditions, etc.
[0036] iv. Perforated holes disposed on ridges and grooves, where the holes are at an angle relative to normal, where the angle is preferably from 30° to 60°, more preferably at 45° to allow easier expulsion of by-product carbon dioxide gas (angled up for anode methanol and down for cathode water) [0037] v. Funnel-shaped or conical-shaped perforated flow field structure, whereby the end of the hole with the larger surface area preferably faces the air or methanol side and the end of the hole with the smaller surface area preferably faces the MEA
side.
[0038] vi. A thin 45° V-groove in the center of the plate to accommodate a current collecting wire of a diameter preferably from about 10 thou to about 30 thou. The V-groove can be either open or cased in depending on the application.
[0039] In a further aspect, the present invention discloses the use of cost effective and non-corrosive polymer-based composite plates with appropriate cell geometry and flow field design for direct methanol micro fuel cell applications.

Brief Description of the Drawings:
[0040] The preferred embodiments of the present invention will be described with reference to the accompanying drawings in which like numerals refer to the same parts in the several views and in which:
[0041 ] Figure 1 shows a collector plate of the present invention with a perforated flat structure.
[0042] Figure 2 shows a second collector plate of the present invention with a ribbed structure with ridges and grooves.
[0043] Figure 3 shows a third collector plate of the present invention with recessed flow field surfaces.
[0044] Figure 4 shows a collector plate of the present invention with angled perforations disposed on ridges and grooves.
[0045] Figure 5 shows a collector plate of the present invention with funnel-shaped and conical-shaped holes.
Detailed Description of the Preferred Embodiments:
[0046] The preferred embodiments of the present invention will now be described with reference to the accompanying figures.
[0047] One aspect of the present invention is directed to the use of graphite-based polymer composite materials, and in particular liquid crystalline polymer (LCP) based graphite composite plates for direct methanol micro fuel cell applications. A
further aspect is the development of optimized cell geometry and flow field designs for these composite plates to achieve comparative or better cell performance with metal plates for air breathing direct methanol micro fuel cell conditions. Different cell geometries and flow field designs are provided for different types of applications of direct methanol micro fuel cell.
[0048] 'The use of graphite-based polymer composites, such as LCP based graphite composite material as the flow field plate for direct methanol micro fuel cell application addresses the corrosion issue associated with metal flow field plates. The LCP polymers used as binder material for conductive graphite are hydrophobic in nature and are chemically stable. Therefore, they are not prone to oxidation or corrosion in the presence of either aqueous methanol solution or under oxidative conditions in the fuel cell. Moreover, the LCP polymer does not allow formation of a passive oxidation layer on itself and hence the electrical conductivity of the plate remains unchanged over time.
[0049] The biggest challenge for replacing metal flow field micro fuel cell plates with graphite and polymer composite plates is to reproduce the flow field properties of the ' metal plate within these composite plates. Being thin, the metal plates do not hinder either methanol distribution onto the anode surface or the displacement of product carbon dioxide bubbles away from anode surface. Typically, a composite plate is made thicker than metal plates so that it has enough fractural strength for withstanding the compression force applied on it to get good contact between the MEA and the plate.
[0050] In other aspects of the present invention there is provided different types of flow field structures on a thinner composite plate to enhance reaction kinetics and therefore the performance of the micro fuel cell by allowing good delivery of methanol onto the anode surface and removal of gaseous carbon dioxide by-product away from the anode. Different cell geometries are provided to obtain better compression of the MEA, better methanol distribution, better by-product removal, low cell resistance and better overall performance. Flow field plates integrated with these novel flow field designs for new cell geornetries are disclosed in the present invention.
[0051 ] The collector plates of the present invention are made of graphite-based composite material. The graphite can be either in the form of fibers and/or powders, and the preferred polymer base resin is selected from LCP, thermoset and thermoplastic polymers. Especially preferred are plates made of a LCP polymer and graphite mixture. The LCP polymer acts as a binder for graphite particulates.
Graphite particles provide the desired electrical conductivity in the product for fuel cell applications. Physically, the plate can be molded and/or machined to the desired shape and size.

[0052] US Patent 6379795 issued to E.I du Pont describes the material content and fabrication techniques for these conductive polymer composite plates. The teachings of US Patent 6379795 are hereby incorporated by reference. The plates thus made can be cut into the desired size and machined to incorporate desired flow field structures to them. Alternatively, they can be molded to the desired size and with the desired flow field design. The size and flow field designs on the plate material depends on the desired application of these plates in air breathing direct methanol fuel cells.
[0053] As taught in US Patent 6379795, useful aromatic thermoplastic liquid crystalline polymers include polyesters, polyester-amides), polyester-imides), and polyazomethines. Especially useful are aromatic thermoplastic liquid crystalline polymers that are polyesters or polyester-amides). It is also preferred in these polyesters and polyester-amides) that at least about 50%, more preferably about 75%
of the bonds to ester or amide groups, i.e., the free bonds of --C(O)O-- and --C(O)NR~
-- where Rl is hydrogen or hydrocarbyl, be to carbons atoms which are part of aromatic rings.
[0054] In a preferred embodiment, the polyesters or polyester-amides) are made from monomers such as one or more aromatic dicarboxylic acid such as isophaltic acid, terephtalic acid, 4,4-bibenzoic acid, 2,6-napthalene dicarboxylic acid, one or more aromatic dihydoxy compounds such as hydroquinone, a substituted hydroquinone such as methylhydroquinone, t-butylhydroquinone, and chlorohydroquinone, resorcinol, 4,4'-biphenol, 2,6-napthalenediol, and 2,7-napthalenediol, one or more aromatic hydroxyacids such as 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, and 6-hydroxy-2-napthoic acid and (in the case of poly(ester-amides)) one or more aromatic diamines such as p-phneylenediamine or m-phenylenediamine.
[0055] Included within the definition herein of an aromatic thermoplastic liquid crystalline polymer is a blend of 2 or more aromatic thermoplastic liquid crystalline polymers, or a blend of an aromatic thermoplastic liquid crystalline polymer with one or more non-aromatic thermoplastic liquid crystalline polymers wherein the aromatic thermoplastic liquid crystalline polymer is the continuous phase.

11 [0056] In one embodiment, an aromatic thermoplastic liquid crystalline resin is combined with a conductive, metal-coated, preferably nickel-coated, graphite fiber, formed into pellets by the adhesive action of a thermoplastic resin binder. In the process of the invention, the aromatic thermoplastic liquid crystalline resin is preferably dry mixed, as by tumbling, with the metal-coated graphite fiber pellets to form a coarse homogeneous mixture. The mixture is fed to the feed throat of an injection molding machine and the resins melt as the resin mixture is conveyed along the flights of the screw while the action of the screw causes the fibers to disperse within the aromatic thermoplastic liquid crystalline resin melt. The molten dispersion is fed to a mold in which the melt hardens to form a shaped article that is then ejected from the mold.
[0057] The following examples illustrate the various advantages of the preferred method of the present invention.
Examples:
Example 1:
[OOSB] Example 1: As shown in Fig.l, an LCP-based composite plate 10 was made and cut into a 3.2 cm x 3.2 cm square. The plate was machined to smoothen both the front 12 and back (not shown) surfaces and a plurality of holes 14 were drilled through the plate 10. The diameter of the holes 14 varied from 20 thou (thousandths of an inch) to 100 thou. The overall active area of the plate 10 was S cm2. A
45° V-groove (not shown) with a radius varying between 10 thou to 30 thou was machined in the center of the plate 10. This was done to accommodate a current collecting wire (also not shown): A similar structure was fabricated using a 1.9 cm x 6.4 crn plate, and also possessing an active area of S cm2.
[00S9] Example 2: As shown in Fig. 2, an LCP-based composite plate 20 was made and cut into a 3.2 cm x 3.2 cm square. The plate 20 was machined to smoothen both the front 22 and back 24 surfaces. A ribbed structure 26 was then machined into the plate 20 and holes 28 were drilled through the plate 20. The diameter of the holes 28 varied between 20 thou to 100 thou, depending on the dimension of the ribbed structure 26. The overall active area of the plate 20 was S cm2. A 4S°
V-groove (not

12 shown) with a radius varying between 10 thou to 30 thou was machined in the center of the plate 20. This was done to accommodate a current collecting wire (also not shown). A similar structure was fabricated using a 1.9 cm x 6.4 cm plate, which also possessed an active area of 5 cm2.
[0060] Example 3: As shown in Fig. 3,a third LCP-based composite plate 30 was made and also cut into a 3.2 cm x 3.2 cm square. The plate 30 was machined to smoothen both the front 32 and back 34 surfaces. A recessed active area 36 of 5 cm2 was machined into the plate 30. The depth of the recessed active area 36 relative to the front surface 32 varied between 20 thou to 80 thou depending on the application.
A ribbed structure 38 was then machined into the recessed active area 36 and holes 39 were drilled through the plate 30. The diameter of the holes 39 varied between thou to 100 thou, depending on the dimension of the ribbed structure 36. The overall recessed active area 36 of the plate 30 had an area of 5 cm2. A 45° V-groove (not shown) with a radius varied between 10 thou to 30 thou was machined in the center of the plate 30. This was done to accommodate a current collecting wire (also not shown). A similar structure was fabricated using a 1.9 cm x 6.4 cm plate, which also had an active area of 5 cm2.
[0061 ] Example 4: As shown in Fig. 4, an LCP-based composite plate 40 was made and cut into a 3.2 cm x 3.2 cm square. The plate 40 was machined to smoothen both the front 42 and back (not shown) surfaces and holes 44 were drilled through the plate 40 at an angle that varied from 30° to 60°. The diameter of the holes 44 varied between 20 thou to 100 thou. The overall active area of the plate 40 was 5 cm2. A
45° V-groove (not shown) with a radius varying between 10 thou to 30 thou was machined in the center of the plate 40. This was done to accommodate a current collecting wire (also not shown). A similar structure was fabricated using a 1.9 cm x 6.4 cm plate, which also had an active area of 5 cm2.
[0062] Example 5: An LCP-based composite plate was made and cut into a 3.2 cm x 3.2 cm square. The plate was machined to smoothen both the surfaces. A ribbed structure was then machined into it and holes were drilled through the plate at angles varying from 30° to 60°. The diameter of the holes varied between 20 thou to 100

13 thou, depending on the dimension of the ribbed structure. The overall active area of the plate was 5 cm2. A 45° V-groove with a radius varying between 10 thou to 30 thou was machined in the center of the plate. This was done to accommodate a current collecting wire. A similar structure was fabricated using a 1.9 cm x 6.4 cm plate that possessed an active area of 5 cmZ.
[0063] Example 6: As shown in cross-section in Fig. 5, an LCP-based composite plate 50 was made and cut into a 3.2 cm x 3.2 cm square. The plate 50 was machined to smoothen both the air/methanol surface 52 and the MEA surface 54 and holes 56 of conical or funnel shape were drilled through the plate 50. The cone angle 58 varied from 30° to 60° relative to normal. The diameter of the holes 56 varied between 20 thou to 100 thou. The overall active area of the plate was 5 cm2. A 45°
V-groove (not shown) with a radius varying between 10 thou to 30 tlhou was machined in the center of the plate 50. This was done to accommodate a current collecting wire (also not shown). A similar structure was fabricated using a 1.9 cm x 6.4 em plate that also possessed an active area of S cm2.
[0064] Example 7: An LCP-based composite plate was made and cut into a 3.2 cm x 3.2 cm square. The plate was machined to smoothen both surfaces. A ribbed structure was then machined into the plate and holes of conical or funnel shapes were drilled through the plate. The cone angle varied from 30° to 60°
relative to normal. The diameter of the holes varied between 20 thou to 100 thou, depending on the dimension of the ribbed structure. The overall active area of the plate was 5 cm2. A
45° V-groove with a radius varying between 10 thou to 30 thou was machined in the center of the plate. This was done to accommodate a current collecting wire. A
similar structure was fabricated using a 1.9 cm x 6.4 cm plate having an active area of cm2.
[0065] Although the present invention has been shown and described with respect to its preferred embodiments and in the examples, it will be understood by those skilled in the art that other changes, modifications, additions and omissions may be made without departing from the substance and the scope of the present invention as defined by the attached claims.

Claims

What is claimed is:

1. An electrically conductive current collector plate for use in micro fuel cell applications wherein the plate comprises graphite fibers and/or graphite powder and a polymer resin, preferably the polymer is selected from a liquid crystalline polymer, a thermoset and a thermoplastic polymer, and most preferably the polymer is liquid crystalline polymer.

2. An electrically conductive current collector plate for use in micro fuel cell applications comprising a plurality of holes through the plate, preferably the diameter of the holes varies from about 0.020 inches to 0.100 inches, and more preferably the plate has an overall active area of about 5 cm2.

3. An electrically conductive current collector plate for use in micro fuel cell applications comprising a ribbed structure in the plate and holes through the plate, preferably the diameter of the holes varies from about 0.020 inches to 0.100 inches, and more preferably the plate has an overall active area of about cm2.

4. An electrically conductive current collector plate for use in micro fuel cell applications comprising a recessed active area of preferably 5 cm2 in the plate, wherein the recessed active area had a depth relative to a surface of the plate of preferably from 0.020 inches to 0.080 inches, a ribbed structure in the recessed active area and holes through the plate, preferably the diameter of the holes varies from about 0.020 inches to 0.100 inches, and more preferably the plate has an overall active area of about 5 cm2.

5. An electrically conductive current collector plate for use in micro fuel cell applications comprising a plurality of holes through the plate, preferably the holes are at an angle varying from 30° to 60° relative to normal, and preferably the diameter of the holes varies from about 0.020 inches to 0.100 inches, and more preferably the plate has an overall active area of about 5 cm2.

6. An electrically conductive current collector plate for use in micro fuel cell applications comprising a ribbed structure in the plate and holes through the plate, wherein the holes are at an angle preferably varying from 30° to 60°

relative to normal, and preferably the diameter of the holes varies from about 0.020 inches to 0.100 inches, and more preferably the plate has an overall active area of about 5 cm2.

7. An electrically conductive current collector plate for use in micro fuel cell applications comprising a plurality of holes of conical or funnel shapes through the plate, wherein the holes had a cone angle preferably from 30° to 60° relative to normal, and preferably the diameter of the holes varies from about 0.020 inches to 0.100 inches, and more preferably the plate has an overall active area of about 5 cm2.

8. An electrically conductive current collector plate for use in micro fuel cell applications comprising a ribbed structure in the plate and holes of conical or funnel shapes through the plate, wherein the holes had a cone angle preferably from 30° to 60° relative to normal, and preferably the diameter of the holes varies from about 0.020 inches to 0.100 inches, and more preferably the plate has an overall active area of about 5 cm2.