|Publication number||USRE41577 E1|
|Application number||US 11/998,436|
|Publication date||Aug 24, 2010|
|Filing date||Nov 29, 2007|
|Priority date||Mar 1, 2002|
|Also published as||US6969563|
|Publication number||11998436, 998436, US RE41577 E1, US RE41577E1, US-E1-RE41577, USRE41577 E1, USRE41577E1|
|Inventors||Gerard Francis McLean|
|Original Assignee||Angstrom Power Incorporated|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (41), Non-Patent Citations (6), Referenced by (1), Classifications (21), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The application herein claims priority from the provisional Patent Application 60/360,638 with a filing date of Mar. 1, 2002.
The present invention relates to fuel cells. More specifically the invention relates to methods of combining separate fuel cell layers to form a fuel cell layer structure.
High power density fuel cells have long been desired.
Existing fuel cells generally are a stacked assembly of individual fuel cells, with each cell producing high current at low voltage. The typical cell construction involves reactant distribution and current collection devices brought into contact with a layered electrochemical assembly consisting of a gas diffusion layer, a first catalyst layer, an electrolyte layer, a second catalyst layer and a second gas diffusion layer. With the exception of high temperature fuel cells, such as molten carbonate cells, most proton exchange membrane, direct methanol, solid oxide or alkaline fuel cells have a layered planar structure where the layers are first formed as distinct components and then assembled into a functional fuel cell stack by placing the layers in contact with each other.
One major problem with the layered planar structure fuel cell has been that the layers must be held in intimate electrical contact with each other, which if intimate contact does not occur the internal resistance of the stack increases, which decreases the overall efficiency of the fuel cell.
A second problem with the layered planar structured fuel cell has been to maintain consistent contact between the layers for sealing and ensuring correct flows of reactants and coolants in the inner recesses of the layer structured fuel cell. Also if the overall area of the cell becomes too large then there are difficulties creating the contacting forces needed to maintain the correct fluid flow distribution of reactant gases over the electrolyte surface.
Existing devices also have the feature that, with the layered planar structure fuel cell since both fuel and oxidant are required to flow within the plane of the layered planar structured fuel cell, at least 4 and up to 10 but typically 8 distinct layers have been required to form a workable cell, typically a first flowfield, a first gas diffusion layer, a first catalyst layer, a first electrolyte layer, a second catalyst layer, a second gas diffusion layer, a second flowfield layer and a separator. These layers are usually manufactured into separate fuel cell components and then the layers are brought into contact with each other to form a fuel cell stack. When contacting the layers care must be taken to allow gas diffusion within the layers while preventing gas leaking from the assembled fuel cell stack. Furthermore, all electrical current produced by the fuel cells in the stack must pass through each layer in the stack, relying on the simple contacting of distinct layers to provide an electrically conductive path. As a result, both sealing and conductivity require the assembled stack to be clamped together with significant force in order to activate perimeter seals and reduce internal contact resistance.
The manufacture of the layers for existing fuel cell configurations is often expensive and difficult. The bipolar plates, which serve as oxidant and fuel flowfields as well as the separator are often constructed from graphite which is difficult to machine, adding significant cost to the fuel cell stack. The membrane electrode assembly (MEA) is usually constructed by first coating a solid polymer electrolyte with catalyst on either side and then pressing gas diffusion electrodes onto the electrolyte. The fuel cell assembly requires multiple individual bipolar plates and membrane electrode assemblies to be connected together in a serial manner. Usually discrete seals must be attached between neighbouring bipolar plates and membrane electrode assemblies and the whole stack of sealed bipolar and MEA layers must be held together under considerable compressive force.
A need has existed to develop alternative fuel cell designs that do not perpetuate the approach of assembling discrete layers in a serial manner. One way to meet this need is to build fuel cells using a micro-structured approach wherein micro-fabrication techniques and nano-structured materials can be combined to create novel devices not subject to the problems commonly associated with conventional fuel cell designs. The application of micro-scale techniques to fuel cells has a number of distinct advantages. Specifically, the potential for increased power density due to thinner layers and novel geometries, improved heat and mass transfer, improved and/or more precise catalyst utilization and reduced losses with shorter conductive path lengths will all make fuel cells more efficient and enable higher volumetric power densities. The opportunity to include ancillary systems into the fuel cell design and the potential for new applications to emerge present even more potential benefits.
A need has existed for a micro fuel cell capable of low cost manufacturing because of having fewer parts than the layered planar structure fuel cell.
A need has existed for a micro fuel cell having the ability to utilize a wide variety of electrolytes.
A need has existed for a micro fuel cell, which has substantially reduced contact resistance within the fuel cell.
A number of prior inventions have used microscale-manufacturing techniques with fuel cells. U.S. Pat. No. 5,861,221 presents a ‘membrane strip’ containing a number of conventional MEAs connected to each other in series by connecting the edge of the negative electrode of one MEA to the edge of the positive electrode of the next MEA. Two configurations are considered. The first constructs the ‘membrane strip’ by placing the MEAs together in a step-like configuration. The second constructs the ‘membrane strip’ by combining MEAs end-to-end with electrically conductive regions between them that connect the cells in series. In some follow-up work (U.S. Pat. No. 5,925,477) the same inventors incorporate a shunt between the electrodes to improve the electrical conductivity of the cell. The MEAs themselves are of conventional layered structure design, and the overall edge collected assembly continues to rely on conventional seals between neighbouring MEAs.
U.S. Pat. No. 5,631,099 and U.S. Pat. No. 5,759,721 use similar series connection concepts but apply a number of other micro-scale techniques to the fuel cell design. By doing so multiple fuel cells are formed within a single structure simultaneously. The fuel cells themselves still reside as layered planar devices mounted onto a carrier, with interconnection between neighbouring fuel cells requiring a penetration of the carrier layer. Most of the techniques discussed in these patents relate to the creation of methanol tolerant catalysts and the application of palladium layers to the catalyst to prevent methanol crossover within the cells.
WO 01/95406 describes a single membrane device that is segmented to create multiple MEA structures. Complex bipolar plates that are difficult to manufacture provide both fuel and oxidants to both sides of the MEA layer. U.S. Pat. No. 6,127,058 describes a similar structure, but instead of complex manifolding of reactant gases, only one reactant is supplied to either side of the MEA layer. Series interconnection of the fuel cells formed within the single MEA layer is achieved through external current collectors arranged around the perimeter of the device providing electrical connection from the top of the MEA layer to the bottom of the MEA layer. Such perimeter electrical connections are inefficient.
Some prior art fuel cells attempt to reduce size and fabrication costs by applying micro-fabrication techniques. For example the Case Western Reserve University device forms multiple fuel cells on a carrier substrate using thin layer processes similar to those used in printing and semi-conductor fabrication (Wainwright et al. “A micro-fabricated Hydrogen/Air Fuel Cell” 195 Meeting of the Electrochemical Society, Seattle, Wash.; 1999). In these designs the fuel cells remain of conventional planar design, with the exception that the fuel cells are built-up to a base substrate. The cathodes must be formed on top of the planar electrolytes and then must be connected to neighbouring anodes with an explicit interconnect.
All the cells presented above use current collection on the edge of the electrode. This significantly increases the internal cell resistance of these cells. Each of these cells are also based on solid polymer electrolytes as this is the only electrolyte that allows for easy manufacture. Furthermore, all of the cells presented above achieve a micro fuel cell design by forming multiple fuel cells within a single electrolyte plane.
The concept of using non-planar electrolytes has been considered in the past. GB 2,339,058 presents a fuel cell with an undulating electrolyte layer. In this configuration a conventional layered MEA is constructed in an undulating fashion. This MEA is placed between bipolar plates. This design increases the active area that can be packed into a given volume. However, this design still relies on the expensive and complicated layered structure with explicit seals and requires compressive force to maintain internal electrical contact and sealing. JP 50903/1996 presents a solid polymer fuel cell having generally planar separators with alternating protruding parts serving to clamp a power generation element (apparently an MEA) into a non-planar but piecewise linear shape. As with GB 2,339,058, this document continues to rely on the expensive and complicated layered structure but this design also puts undue stress on the MEA by forcing it into a non-planar arrangement using the separator plates.
In addition to non-planar designs, some prior art presents tubular configurations. U.S. Pat. No. 6,060,188 presents a cylindrical fuel cell with a single MEA layer formed into a cylinder. Fuel or oxidant is delivered to the interior recess of the cylinder with the other reactant delivered on the exterior. Within this design, each cylindrical structure creates a single cell, with current flowing through the annular cylindrical wall that is the fuel cell. A method of providing series electrical interconnection between fuel cells or of sealing individual fuel cells is not disclosed. This design is reminescent of tubular designs for solid oxide fuel cells that are well known.
U.S. Pat. Nos. 5,252,410 and 4,037,023 and JP 6-3116369 present designs that form flow channels directly into the porous carbon gas diffusion electrode layers of the MEA. This approach does not get away from the essentially planar structure of the MEA or the flow field and separator plate but rather puts the gas distribution layer into the GDE rather than into the separator plate. Although this can decrease the cost the final structure is still a conventional layered structure fuel cell with a simple rearrangement of the layers. The ability to form flow fields into the fuel cell layer structure and create a fuel cell without the need for separator between layers is not discussed.
A need has existed to develop fuel cell topologies or fuel cell architectures that allow increased active areas to be included in the same volume, i.e. higher density of active areas. This will allow fuel cells to be optimized in a manner different than being pursued by most fuel cell developers today.
The present invention relates to methods of combining separate fuel cell layers to form a fuel cell layer structure. A number of features of the fuel cell layers are unique and allow for much simpler stacking structures.
More specifically, the present invention contemplates a multiple fuel cell structures with a plurality of fuel cell layers, each fuel cell layer comprising an anode side and a cathode side, a positive end and a negative end. The first fuel cell layer is stacked on top of a second fuel cell layer such that the anode side of the first fuel cell layer and the anode side of the second fuel cell layer adjoin. Additional fuel cells layers can then be disposed on the fuel cell layers in a like manner. The invention also has at least one seal disposed between the adjacent fuel cell layers forming at least one plenum and a positive connector and a negative connector for connecting the stack to the outside load. When fuel is presented to the anode sides of the plurality of fuel cell layers and oxidant is presented to the cathode sides of the plurality of fuel cell layers, a current is produced to drive the outside load.
In this embodiment optional formed flow fields can be created on the fuel cell layers. Alternately, the at least one plenum created by the at least one seal can be solid with a flow field. The plenum can also comprise a permeable material. The fuel cell layers of the multiple fuel cell structure can be connected in series, in parallel, or in combinations thereof between the positive and negative electrical connectors.
This configuration achieves the functionality of a conventional stack structure without the requirement for any explicit multi-function or bipolar separator plate to be inserted between discrete fuel cells or fuel cell layers resulting in an overall more space and material efficient design. Furthermore, since there is no current flow between neighbouring fuel cell layers the task of sealing and connecting the fuel cell layers into the stack is simplified considerably. Forming the flow fields on the surface of the fuel cell layers allows the reactant distribution flow paths to be formed without significantly decreasing the total reactive area of the fuel cell stack in comparison to an embodiment constructed without the formed flow fields.
The invention further contemplates a bi-level fuel cell layer structure comprising: a first fuel cell layer and a second fuel cell layer, each fuel cell layer comprising an anode side and a cathode side, a positive end and a negative end, and wherein the first fuel cell layer is stacked on top of the second fuel cell layer such that the anode side of the first fuel cell layer and the anode side of the second fuel cell layer adjoin forming a bi-level stack; a seal disposed between the first and second fuel cell layers forming a fuel plenum; a positive connector for connecting the bi-level stack to an outside load; and a negative connector for connecting the bi-level stack to the outside load; such that when fuel is introduced to the fuel plenum and the cathode sides are exposed to an oxidant, current is produced to drive the outside load.
The individual fuel cell layers in the bi-level fuel cell layer structure can be connected in either parallel or in series. The resulting structure is an enclosed plenum air breathing fuel cell that achieves a series electrical connection of the individual fuel cells in each fuel cell layer. Only fuel is required to be fed to the interior of the structure and electrical current flows within the two fuel cell layers independently of one another. There is no electrical connection between the two fuel cell layers except at the positive and negative electrical connections at either end of the fuel cell layers in the structure.
An optional solid material with a flow field can be disposed in the plenum created by the first and second fuel cell layers and the seal. The plenum could also comprise a permeable material or a hydrogen storage material. Alternately pressurized hydrogen or a liquid fuel could be stored within the plenum. It is also envisioned that the plenum be open to the ambient environment.
The fuel cell layers within the bi-level fuel cell structure can also comprise formed flow fields for the controlled delivery of reactant gases to the layers.
A specific embodiment of the invention will be described by way of example with reference to the accompanying drawings, in which:
The present invention relates to a microstructure fuel cell having a substrate, which is preferably porous, an assembly of fuel cells having a single or multiple substrate structure and methods for manufacturing such fuel cells and fuel cell layers.
The invention relates to a specific fuel cell architecture that is of an integrated design in which the functions of gas diffusion layers, catalyst layers, and electrolyte layers are integrated into a single substrate. This architecture makes it possible to fold together the various ‘layers’ of which a working fuel cell is formed and produce linear, curvilinear, undulating or even fractal shaped electrolyte paths that allow for higher volumetric power density to be achieved by increasing the electrochemically active surface area. In addition, by forming the various fuel cell layers within a single substrate the problem of simple contacting of fuel cell components to create electrical connections is eliminated, thus creating the potential for lower internal cell resistances to be achieved. The cell layers themselves can be constructed in planar, non-planar or involute configurations providing further advantages in increasing surfaces areas and providing flexibility in applications. This integrated design enables simpler manufacturing processes and scaling of the design.
Unlike existing fuel cell designs, the present invention, in one embodiment, provides convoluted electrolyte layers, which do not smoothly undulate. Other embodiments of the invention include shapes that are essentially non-smooth. Utilizing such non-smooth electrolyte paths allows for greater overall surface areas for the fuel cell reactions to be packed into a given volume that can be achieved when planar electrolyte layers are employed as in conventional fuel cell designs. The present invention also allows for significantly decreased distances between separate electrolyte layers, thereby allow for a greater surface area in a given volume than conventional designs.
The present invention contemplates the use of a design inspired by fractal patterns, which provides long electrolyte path lengths. The invention includes a method for building fuel cells and “stacks” that are not dependent on the layered process and which do not require the post-manufacturing assembly of distinct layered components. The conventional relationship between MEA layers and bipolar plates is eliminated, as is the reliance on multiple discrete layered structures. The invention also contemplates a design with individual fuel cells turned on their side relative to the overall footprint of the assembled fuel cell device. The invention contemplates building multiple fuel cells with an integrated structure on a single substrate using parallel manufacturing methods.
Specifically, it is contemplated to use a porous substrate for the fuel cell through which reactant gas will diffuse with little driving force. The substrate may or may not be electrically conductive. If it is conductive, it is contemplated to insulate at least a portion of the substrate, which typically would separate the anode from the cathode, this insulation may be formed by the electrolyte separating the anode from the cathode and, if necessary, an optional insulating structural member may be added. More specifically, the fuel cell is contemplated to have: (a) a fuel plenum comprising fuel; (b) an oxidant plenum comprising oxidant; (c) a porous substrate communicating with the fuel plenum, and the oxidant plenum further comprising a top, a bottom, a first side, and a second side; (d) a channel formed using the porous substrate, wherein the channel comprises a first channel wall and a second channel wall; (e) an anode formed from a first catalyst layer disposed on the porous substrate of the first channel wall; (f) a cathode formed from a second catalyst layer disposed on the porous substrate of the second channel wall; (g) electrolyte disposed in at least a portion of the channel contacting the anode and the cathode preventing transfer of fuel to the cathode and preventing transfer of oxidant to the anode; (h) a first coating disposed on at least a portion of the porous substrate to prevent fuel from entering at least a portion of the porous membrane; (i) a second coating disposed on at least a portion of the porous substrate to prevent oxidant from entering at least a portion of the porous substrate; (j) a first sealant barrier disposed on the first side and the second sealant barrier disposed on the second side; (k) a positive electrical connection disposed on the first side; (l) a negative electrical connection disposed on the second side; and wherein the resulting fuel cell generates current to drive an external load.
The porous substrate 12 can have a shape that is rectangular, square or orthogonal or alternatively, it can be irregularly shaped. In this embodiment it is pictured as being formed within a single plane, although non-planar substrates or multiple substrate configurations are envisioned.
A channel 14, formed using the porous substrate, can be straight or of arbitrary design. If of arbitrary design the channel is referred to throughout this application is “undulating.” If multiple channels are present at least one may be undulating. The channel 14 has a first channel wall 22 and a second channel wall 24. Additionally the porous substrate 12 has a top 100, bottom 102, first side 104 and a second side 106.
The channel can comprise an undulating channel, a straight channel or an irregular channel. If undulating, the channel can be sinusoidal in shape and if undulating, the channel may be of a shape that is in at least three planes.
An anode 28 is created on or alternately in the surface of the first channel wall 22, although the anode could be embedded in the wall as well. Anode 28 is created using a first catalyst layer 38 on or into the surface of the first channel wall 22.
A cathode 30 is formed on the surface or alternately in the second channel wall 24. Like the anode 28, the cathode 30 could be embedded in the second channel wall 24. Cathode 30 is created using a second catalyst layer 40.
The catalyst layers can be deposited on the first and channel walls or can be formed in the channel walls. In one embodiment the first and second catalyst layers are disposed in the porous substrate to at least a minimum depth to cause catalytic activity.
Referring back to
A first coating 34 is disposed on at least a portion of the porous substrate 12 preventing fuel from entering at least a portion of the porous substrate 12. A second coating 36 is disposed on at least a portion of the porous substrate 12 preventing oxidant from entering at least a portion of the porous substrate 12.
A first sealant barrier 44 is disposed on the first side of the porous substrate and a second sealant barrier 46 is disposed on the second side of the porous substrate. The sealant barriers can optionally be disposed within a sealant barrier channel 43.
A positive electrical connection 50 is engaged with the porous substrate 12 on the first side of the porous substrate.
A negative electrical connection 48 is engaged with the porous substrate 12 on the second side of the porous substrate.
The resulting fuel cell generates current 56 to drive an external load 58.
In one version of this embodiment of the invention, it is contemplated that the electrolyte 32 can be mounted in the channel 14 at an angle 76, preferably at an angle, which is perpendicular to the longitudinal or horizontal axis 74 of the predominant portion of the porous substrate 12.
Now referring to
In this embodiment it is envisioned that the fuel cell be connected in series, in parallel or in combinations thereof to allow the fuel cell layer to produce current to drive an external load.
It is understood that the same embodiments shown for the multiple substrate structure in
This association of two fuel cells, either by the structure of
The association of multiple fuel cells produces a fuel cell layer 64 having a fuel side 116 that is brought into association with a fuel plenum 10 and an oxidant side 118 that is brought into association with an oxidant plenum 16.
If the substrate material from which the fuel cells within the fuel cell layer 64 is formed is conductive, then electrical current produced by the individual fuel cells is able to flow directly through the substrate material and the sealant barriers 44 to create a bipolar fuel cell structure within the formed fuel cell layer. If the substrate material from which the fuel cells within the fuel cell layer are formed is not electrically conductive than the first coating 34 and second coating 36 should both be made of an electrically conducting material and formed so that the first coating 34 is in electrical contact with the second catalyst layer 40 while second coating 36 is in electrical contact with the first catalyst layer 38. The first coating 34 and the second coating 36 are also made in electrical contact with the conductive sealant barrier 44. In either case, with a conductive or non-conductive substrate the electrical current produced by the fuel cell can be transported to the positive and negative electrical connections.
An alternate configuration for the fuel cell layer is shown in FIG. 5a. In this configuration the first coating 34 is extended to connect the anode of the first fuel cell to the cathode of the second fuel cell. The second coating 36 is likewise extended to contact the anode of the first fuel cell. The first coating on the end of the second coating on the end can be used to connect the fuel cells on the ends to the positive electrical connection 50 and the negative electrical connection 48. In this configuration portions of the first coating are porous to allow fuel to reach the anode and portions of the second coating are porous to allow oxidant to reach the cathode. In this configuration neither the porous substrate nor the sealant barrier need be electrically conductive. It is also envisioned that only the first coating be extended to provide electrical contact between the cells or that only the second coating be extended to provide electrical contact between the cells.
When multiple fuel cells are formed into a fuel cell layer, as described in
The overall structure of the fuel cell layer 64 creates a series connection of the individual fuel cells. Positive electrical connection 50 and negative electrical connection 48 allow an external load to be connected to the fuel cell layer, which produces a voltage that is a multiple of the single cell voltages produced within the fuel cell layer.
Although only cylindrical cells have been shown enclosing a volume it is contemplated herein that shapes such as extruded rectangles, squares, ovals, triangles and other shapes as well as non-extruded shapes such as cones, pyramids, football shaped objects and other shapes that enclose a volume are included as part of the invention.
In this Figure, a seal 130 is disposed between the first and second fuel cell layer to form a fuel plenum 124. The two positive electrical connections are connected to positive connector 120 and the two negative electrical connections are connected to negative connector 122 so that the individual fuel cell layers are now connected in an electrically parallel configuration. The resulting assembly is a bi-level fuel cell layer structure 254 having a top 70 and a bottom 72, the top and bottom being the cathode sides of the respective fuel cell layers. The resulting structure is an enclosed plenum air breathing fuel cell that achieves a series electrical connection of the individual fuel cells in each fuel cell layer and a parallel electrical connection of the two fuel cell layers. Only fuel is required to be fed to the interior of the structure and electrical current flows within the two fuel cell layers independently of one another. There is no electrical connection between the two fuel cell layers except at the parallel connection of the positive and negative electrical connections at either end of the fuel cell layers in the structure.
An optional solid material with a flow field (not shown in this figure) can be disposed in the plenum 124 created by the first and second fuel cell layers 64, 112 and the seal 130. The plenum could also comprise a permeable material or a hydrogen storage material. Alternately pressurized hydrogen or a liquid fuel could be stored within the plenum. It is also envisioned that the plenum be open to the ambient environment. The connectors can also be disposed in such a manner as to connect the layers in series rather than in parallel. p
Both configurations of the bi-level fuel cell layer structure form a stand-alone electrical power-generating device with a parallel connection of the two fuel cell layers doubling the power output of the structure compared to the individual layers.
When reactant is delivered to the fuel cell structure from some external source and is flowed through the fuel cell layers it is desirable to control the flow of the fuel over the fuel cell layer.
In both the FIG. 15 and the
In the foregoing paragraphs a method of forming a fuel cell layer structure by electrically connecting multiple fuel cell layers in parallel and by forming reactant distribution flow fields within the individual fuel cell layers has been described. This configuration achieves the functionality of a conventional stack structure without the requirement for any explicit multi-function or bipolar separator plate to be inserted between discrete fuel cells or fuel cell layers resulting in an overall more space and material efficient design. Furthermore, since there is no current flow between neighbouring fuel cell layers the task of sealing and connecting the fuel cell layers into the stack is simplified considerably. Forming the flow fields on the surface of the fuel cell layers allows the reactant distribution flow paths to be formed without significantly decreasing the total reactive area of the fuel cell stack in comparison to an embodiment constructed without the embossed flow fields. Extra volume for separate bipolar plates, separators, etc. is not required with this configuration providing an overall increase in the volumetric power density of the fuel cell stack.
Although various materials could be used for the porous substrate of the invention, one usable material could be a conductive material. Materials such as a metal foam, graphite, graphite composite, at least one silicon wafer, sintered polytetrafluoroethylene, crystalline polymers, composites of crystalline polymers, reinforced phenolic resin, carbon cloth, carbon foam, carbon aerogel, ceramic, ceramic composites, composites of carbon and polymers, ceramic and glass composites, recycled organic materials, and combinations thereof are contemplated as usable in this invention.
The channel is contemplated to have up to 50 optional support members separating the walls of the channel. The support members can be located at the extreme ends of the channel, such as forming a top or bottom, or can be located in the middle portion of the channel, or be oriented at an angle to the center of the channel. It is contemplated that the support member can be an insulating material. If an insulating material is used, it is contemplated that silicon, graphite, graphite composite, polytetrafluoroethylene, polymethamethacrylate, crystalline polymers, crystalline copolymers, cross-linked polymers thereof, wood, and combinations thereof can be usable in the invention.
Dimensionally, the channel can have a dimension ranging from 1 nanometer to 10 cm in height, 1 nanometer to 1 mm in width and from 1 nanometer to 100 meters in length.
A single fuel cell of the invention, optionally within a fuel cell layer, is contemplated of being capable of producing between approximately 0.25 volts and approximately 4 volts. Between 1 and 5000 fuel cells are contemplated as usable in one fuel cell layer in this design, however in a preferred embodiment, the fuel cell layer has between 75 and 150 joined fuel cells. This fuel cell layer is contemplated to be capable of producing a voltage between 0.25 volts and 2500 volts. A fuel cell with more channels will be capable of producing higher voltages.
The invention can be constructed such that the fuel comprises a member of the group: pure hydrogen, gas containing hydrogen, formic acid, an aqueous solution comprising a member of the group: ammonia, methanol, ethanol and sodium borohydride, and combinations thereof. The invention can be constructed such that the oxidant comprises a member of the group: pure oxygen, gas containing oxygen, air, oxygen enriched air, and combinations thereof.
Electrolyte usable in this invention can be a gel, a liquid or a solid material. Various materials are contemplated as usable and include: a perfluoronated polymer containing sulphonic groups, an aqueous acidic solution having a pH of at most 4, an aqueous alkaline solution having a pH greater than 7, and combinations thereof. Additionally, it is contemplated that the electrolyte layer can be between 1 nanometer and 1.0 mm in thickness, or alternatively simply filling each undulating channel from first wall to second wall without a gap.
The fuel cell is manufactured using a first and second coating on the porous substrate. These coatings can be the same material or different materials. At least one of the coatings can comprise a member of the group: polymer coating, epoxies, polytetrafluoro ethylene, polymethyl methacrylate, polyethylene, polypropylene, polybutylene, and copolymers thereof, cross-linked polymers thereof, conductive metal, and combinations thereof. Alternatively, the first or second coating can comprise a thin metallic layer such as a coating of gold, platinum, aluminum or tin as well as alloys of these or other metals or metallic combinations.
The first and second catalyst layers that are contemplated as usable in the invention can be a noble metal, alloys comprising noble metals, platinum, alloys of platinum, ruthenium, alloys of ruthenium, and combinations of these materials. It is contemplated that ternary alloys having at least one noble metal are usable for good voltage creation. Platinum-ruthenium alloys are also contemplated as usable in this invention. The catalyst layers should each have a catalyst loading quantity wherein the amount of catalyst may be different for each layer.
The material for the optional sealant barriers contemplated herein can be selected from the group comprising: silicon, epoxy, polypropylene, polyethylene, polybutylene, and copolymers thereof, composites thereof, and combinations thereof.
One method for making the fuel cell contemplates the following steps:
The sequence of operations described may be varied and steps combined as required to suit the particular material requirements and fabrication processes used. As well, the method can comprise forming between one and 250 or more channels in the porous substrate.
Another method for forming a fuel cell envisioned in the invention contemplates the following steps:
The positive electrical connections and the negative electrical connections of the fuel cells within the fuel cell layer can be connected in series, in parallel or in a combination of series and parallel.
Yet another method for making a fuel cell layer is contemplated which has the steps of:
In any of the methods described above a number of different methods of forming the porous substrate are contemplated herein. The porous substrate can be formed by a method that is a member of the group comprising: casting and then baking, slicing layers from a pre-formed brick, molding, extruding, and combinations thereof. The formed porous substrate may be non-planar or enclose a volume.
If at least one of the coatings is deposited with thin film deposition techniques, the technique may include a member of the group comprising: sputtering, electroless plating, electroplating, soldering, physical vapor deposition, chemical vapor deposition. If at least one of the coatings is an epoxy coating the coating can be disposed on the substrate by a method selected from the group: screen printing, ink jet printing, spreading with a spatula, spray gun deposition, vacuum bagging and combinations thereof. A mask can be used when applying the coatings to the porous substrate. If required, a portion of the coating can be removed prior to adding the electrolyte.
The channel can be formed in the porous substrate by a method selected from the group comprising: embossing, ablating, etching, extruding, laminating, embedding, melting, molding, cutting, and combinations thereof. If etching is used, the etching can be by a method selected from the group comprising: laser etching, deep reactive ion etching, and alkaline etching. Alternatively, it is anticipated the channels can be formed by micro-milling using laser cutting, high pressure water jets, micro-dimensioned rotary tools or mechanical dicing saws.
Within the invention it is envisioned to deposit the electrolyte in the channel using a method that is a member of the group comprising: pressure injection, vacuum forming, hot embossing, and combinations thereof.
The variations for making the apparatus can be implemented into any of the methods described above. For example, the method can contemplate using a conductive material for the sealant barrier and/or an insulation material for the support member.
The fuel cell of the invention can be used by first, connecting a fuel source to a fuel plenum inlet; second, connecting a fuel plenum outlet to a re-circulating controller; third, connecting an oxidant plenum inlet to an oxidant source; fourth, connecting an oxidant plenum outlet to a flow control system, fifth, connecting a positive electrical connection and a negative electrical connection to an external load; sixth, flowing fuel and oxidant to the inlets; and finally, driving load with electricity produced by the fuel cell.
If a dead-ended version of the fuel cell is used the operation is much simpler. First, the fuel inlet is connected to a fuel supply, second, the oxidant inlet is connected to an oxidant supply, third, the positive electrical connection and the negative electrical connection are connected to an external load; and finally, the load is driven with electricity produced by the fuel cell.
The method of the invention can further comprise the step of sealing the plenum outlets and inlets after the fuel and oxidant is loaded into their respective plenums creating a dead ended fuel cell. The fuel cell can then be connected to an external load using the positive and negative electrical connections and used to drive the external load.
It is envisioned within this invention to use any combination of fuel and oxidant inlets and outlets to operate the fuel cell.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US20080187816 *||Jan 30, 2008||Aug 7, 2008||Canon Kabushiki Kaisha||Fuel cell unit and fuel cell|
|International Classification||H01M8/10, H01M8/02, H01M8/24|
|Cooperative Classification||H01M8/1007, H01M8/241, H01M8/0271, Y02E60/50, H01M8/006, H01M8/004, H01M8/0247, H01M8/2415, H01M8/025|
|European Classification||H01M8/00B4, H01M8/00B2, H01M8/02C6A, H01M8/02C6, H01M8/24B2, H01M8/24B2E, H01M8/02D, H01M8/10B|
|Feb 21, 2008||AS||Assignment|
Owner name: ANGSTROM POWER INC., CANADA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MCLEAN, GERARD F;REEL/FRAME:020545/0907
Effective date: 20080214
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|Dec 30, 2011||AS||Assignment|
Owner name: SOCIETE BIC, FRANCE
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ANGSTROM POWER INCORPORATED;REEL/FRAME:027464/0783
Effective date: 20111129
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|Aug 6, 2015||AS||Assignment|
Owner name: INTELLIGENT ENERGY LIMITED, ENGLAND
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Effective date: 20150604