FUEL CELL SUB-ASSEMBLY
Disclosed herein are aspects of methods, systems, and devices forming fuel cell sub-assemblies including placing a gasket with a peripheral seal defining a central aperture of the gasket on at least one of an anode flow plate and a cathode flow plate then placing a gas diffusion layer having less rigidity than the gasket within said within said central aperture wherein the gas diffusion layer is substantially uniformly spaced by a predetermined spacing from the inside facing surface of the gasket for forming a gallery.
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This application is a Continuation of U.S. patent application Ser. No. 15/761,345, filed Mar. 19, 2018 entitled FUEL CELL SUB-ASSEMBLY, which is a US National 371 Application of PCT/GB2016/052964, filed on Sep. 23, 2016, which claims priority to Great Britain Application No. 1517245.5, filed Sep. 30, 2015.
BACKGROUND OF THE DISCLOSURE Field of the DisclosureThe invention relates to a fuel cell sub-assembly, and in particular to a combination of a gasket and a gas diffusion layer. It also relates to a fuel cell and a fuel cell stack incorporating the fuel cell sub-assembly. A method of assembling a fuel cell is also disclosed.
Related ArtIn fuel cells, an oxidant fluid is directed across the cathode side of each fuel cell, so that oxidant is available to the cathode side of a proton exchange membrane or membrane-electrode assembly (MEA) of the fuel cell, typically via a diffusion layer. Further, a fuel is directed across the anode side of each fuel cell, so that fuel is available to the anode side of the MEA of the fuel cell, typically via a diffusion layer. The diffusion layer is of a porous material to allow the fuel or oxidant to diffuse therethrough as it flows to the MEA. Thus, an inlet channel may be configured to introduce the fuel or oxidant into the diffusion layer and an outlet channel may be configured receive any un-reacted fuel or oxidant or reaction by-products from the diffusion layer.
DISCLOSURE Aspects of some exemplary implementations of systems, device and methods forming of a fuel cell sub-assembly include placing a gasket with a peripheral seal defining a central aperture of the gasket on at least one of an anode flow plate and a cathode flow plate; placing a gas diffusion layer having less rigidity than the gasket within said within said central aperture; and, wherein the gas diffusion layer is substantially uniformly spaced by a predetermined spacing from the inside facing surface of the gasket for forming a gallery.
Aspects of some exemplary implementations of systems, device and methods forming of a fuel cell sub-assembly include a fuel cell sub-assembly comprising:
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- a gasket comprising a peripheral seal for a fuel cell assembly, the peripheral seal defining a central aperture of the gasket;
- a gas diffusion layer for providing diffused gases to a proton exchange membrane of a fuel cell, the gas diffusion layer located within the central aperture;
- wherein at least one connection point, an inside facing surface of the peripheral seal of the gasket is welded to a corresponding outward facing surface of the gas diffusion layer.
The sub-assembly is advantageous as it may simplify manufacture of a fuel cell incorporating the fuel cell sub assembly. The gas diffusion layer may be configured to lie at least partly within the plane of the gasket and may be wholly within the bounds of the central aperture. The weld at the connection point has been found to securely hold the sub-assembly together without substantially interfering with the sealing properties of the gasket. Further, the weld, which may comprise an ultrasonic weld or a laser weld, may allow for intermingling of gasket material with the porous gas diffusion layer.
Optionally, the gas diffusion layer is configured to substantially fill the central aperture. The gas diffusion layer may be configured to be thicker than the gasket (in a direction perpendicular to the plane of the gasket and the gas diffusion layer) when uncompressed.
Optionally, the gas diffusion layer is substantially planar having a first major face, a second major face opposite the first major face and a plurality of surfaces between the first and second major faces, the connection point located on at least one of said plurality of surfaces.
Optionally, the gas diffusion layer, except at the or each connection point, is substantially uniformly spaced by a predetermined spacing from the inside facing surface of the gasket for forming a gallery. By presenting a spacing between the gasket and the gas diffusion layer, the sub-assembly may provide for unimpeded gas flow around the gas diffusion layer such that the gas diffusion layer can receive gas from one or more sides. The gas diffusion layer may or may not include spacing tabs to maintain the spacing during assembly. In some examples, the presence of the weld may obviate the need for any spacing tabs.
Optionally, the gasket includes a channel extending from its inside facing surface into the peripheral seal for providing a fluid connection to a fluid transfer conduit (when assembled) and the at least one connection point is adjacent the channel The channel may be an outlet channel or an inlet channel Providing the or each connection point adjacent an outlet channel may be advantageous for guiding fluid out of the gas diffusion layer and into the channel
Optionally, the sub-assembly includes at least two distinct connection points where the gasket is welded to the gas diffusion layer, the connection point located adjacent the channel, one either side thereof. Having the connection points either side of the channel or a gallery around the channel may advantageously guide fluid flow to/from the gas diffusion layer from/into the channel
Optionally, the gas diffusion layer is substantially rectangular defined by four outwardly facing surfaces and the central aperture is substantially rectangular defined by four inwardly facing surfaces of the peripheral seal, and the or each connection point is located between a particular one of the four surfaces of the gas diffusion layer and a particular one of the four surfaces of the gasket.
Optionally, the gas diffusion layer is of a porous material having spaces between gas diffusion layer material, and at the or each connection point, material of the gasket is comingled with the material of the gas diffusion layer. The gasket may be of one or more of a polymeric material, a plastics material, a natural or synthetic rubber material or any other suitable material that may be welded. The gasket may be flowable when subject to welding energy, such as ultrasonic welding energy.
Optionally, at the or each connection point, the material of the gasket tapers as it extends into the gas diffusion layer and comingles with the gas diffusion layer material. Thus, the thickness of gasket may narrow, at the connection point, as its material extends into the pores/gaps/spaces of gas diffusion layer.
Optionally, the gas diffusion layer and the gasket are substantially planar and a thickness of the gas diffusion layer is greater than a thickness of the gasket and, at the or each connection point, the comingled gasket material and gas diffusion layer material is provided over only part of the thickness of the gas diffusion layer. Thus, in its uncompressed form, the gas diffusion layer may be joined over only a portion of its thickness, which may be a portion adjacent to one major face or in a central region between its major faces.
Optionally, the gasket is substantially planar and has a first major face, a second major face opposite the first major face, the separation between the first and second major faces defining the thickness of the gasket and wherein the comingled gasket material and gas diffusion layer material extends substantially between planes defined by the first and second major faces of the gasket.
Optionally, the comingled material extends solely between the planes.
Optionally, the gasket is;
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- i) an anode gasket for sealing between an anode flow plate and a proton exchange membrane; or
- ii) an cathode gasket for sealing between a cathode flow plate and a proton exchange membrane.
The anode flow plate and/or cathode flow plate may comprise a bipolar flow plate.
Optionally, the gasket is an anode gasket and the sub-assembly includes an anode flow plate configured to provide an anode gas to the gas diffusion layer, the gasket and the gas diffusion layer configured to lie against a face of the anode flow plate.
The anode flow plate may be configured to provide anode gas to the by virtue of a delivery conduit formed therein and/or flow channels to carry the anode gas over the gas diffusion layer, such as over a major face of the gas diffusion layer.
According to a an aspect we provide a fuel cell comprising a proton exchange membrane, an anode flow plate configured to provide an anode gas to an anode gas diffusion layer and a cathode flow plate configured to provide an cathode gas to a cathode gas diffusion layer, wherein the fuel cell includes at least one fuel cell sub-assembly of the first aspect, the gas diffusion layer of the fuel cell sub-assembly forming said anode gas diffusion layer or said cathode gas diffusion layer.
According to a an aspect we provide a fuel cell stack comprising a plurality of fuel cells as defined in the second aspect arranged together in a stack.
According to an aspect we provide method of assembling a fuel cell using the fuel cell sub-assembly of the first aspect, comprising the steps of;
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- receiving an anode flow plate having the fuel cell sub assembly arranged thereon;
- applying a proton exchange membrane to the fuel cell sub assembly on an opposed side to the anode flow plate;
- applying a further fuel cell sub-assembly to the proton exchange membrane;
- applying a cathode flow plate to the further fuel cell sub-assembly on an opposed side to the proton exchange membrane.
Aspects and embodiments of the invention are described in further detail below by way of example and with reference to the enclosed drawings in which:
A fuel cell may be formed from a plurality of layers that may be arranged and optionally compressed together to form a fuel cell having sealed volumes either side of an MEA for receipt of oxidant and fuel. The sealed volumes typically include a gas diffusion layer comprising a porous material to aid the diffusion of oxidant or fuel across the whole area of the respective sides of the MEA. The plurality of fuel cell layers may include an MEA for forming an electrochemical reaction site; a catalyst layer for catalysing the reaction; a gas diffusion layer (GDL) (which may include a microporous layer) for aiding diffusion of fuel or oxidant; a fuel cell plate for separating individual fuel cells in a stack; bipolar plates for providing an electrically conductive connection between fuel cells in a stack; and gaskets for forming seals between the other layers.
Typically, the layers of the fuel cell are thin and require careful handling when assembling the layers to form a fuel cell. Providing a sub-assembly of two or more of layers that form the fuel cell may be advantageous.
The gas diffusion layer is of a porous material and may comprise a heterogeneous matrix of GDL material and air gaps. The GDL may be fibrous having air gaps between the fibres in which the oxidant or fuel may flow. In other examples the GDL may be an open cell foam material. The gas diffusion layer 104 is substantially planar having a first major face 110, a second major face 111 opposite the first major face 110 and a plurality of surfaces (or “sides”) 108, 112, 113, 114 between the first and second major faces 110, 111. The separation between the first and second major faces defines the thickness, TGDL, of the gas diffusion layer. The planar gas diffusion layer 104 is substantially rectangular with the four sides of the rectangle provided by the four outwardly facing surfaces 108, 112, 113, 114.
The gasket 101 is substantially planar and has a first major face 115 and a second major face 116 opposite the first major face. The separation between the first and second major faces 115, 116 defines a thickness of the gasket, Tgasket. The major faces 115, 116 of the gasket are configured to seal against the other layers of the fuel cell when assembled. The gasket 101 comprises a continuous ring, which in this example is a substantially rectangular ring. The ring shape defines the central aperture 103. Accordingly, the height of the inwardly facing surface 107 and another three inwardly facing surfaces 117, 118, 119, that extend between the major faces 115, 116, form the rectangular shape and define the thickness of the gasket 101. It will be appreciated that the gasket may have other shapes, which may be ring shaped or not.
The GDL 104 is arranged in the plane of the gasket. The GDL 104 substantially fills the central aperture 103. In particular, the GDL 104 is joined to the gasket along only one of its side surfaces, namely surface 108. Likewise, the gasket 101 is joined to the GDL along only one of its side surfaces, namely surface 107. Along the other surfaces, the GDL 104 and the gasket 101 are separated by a separation distance, w. Thus, surfaces 113 and 118; 114 and 119; 112 and 117 are separated by separation distance w. The separation distance w is small relative to the width of the GDL 104 and may comprise less than 5 mm, 2 mm or 1 mm. The separation between the GDL 104 and the gasket 101 is provided to form a gallery to allow oxidant or fuel introduced into the central aperture (when assembled with the fuel cell layers) to flow around the GDL and permeate into it from multiple sides 112, 113, 114. This may be advantageous as typically the fuel or oxidant is introduced from one or more channels 120 formed in the plates (not shown) at an edge and around which the gasket seals. Thus, an inlet channel 125 in the gasket 104 provides for transfer of fuel or oxidant from the channel 120 to the GDL 104. It will be appreciated that the gasket and the GDL may be welded over two sides, three sides, four sides or any other number of sides.
The GDL 104, in this example, includes alignment tabs 121, 122, 123 and 124 to position the GDL 104 within the central aperture to provide the separation distance, w. The alignment tabs may extend from the side surfaces 113 and 114 to contact respective inwardly facing surfaces 118, 119 of the gasket 101.
The gasket 101 may include one or more outlet channels 126 that extend outwardly from one or more of the inwardly facing surfaces 107, 117, 118, 119. The channel(s) provide for transfer of fuel or oxidant from the GDL 104 to a channel 127 in the plates (not shown), which the gasket 101 is configured to seal around when assembled with the plates. The GDL 104 is positioned relative to the gasket 101 such that the GDL 104 is spaced from the surface 107 at the mouth of the channel 126 to form an outlet gallery 128. The outlet gallery 128 is bounded on either side by the connection points 105, 106. Such an arrangement of the gallery 128 and the connection points 105, 106 either side thereof has been found to be advantageous in guiding fuel or oxidant into the channels 126, 127. It is also advantageous that the connection points 105, 106 are formed on the same surface 107 of the gasket 101 as the one or more channels 126.
Turning to
While in this example an ultrasonic weld is provided, in other examples, a laser weld may be used. Translation of the laser may encourage molten gasket material to flow towards the GDL 104.
In
While in the above examples, the gasket and GDL are substantially flat members that lie in a plane, they may be curved or of other shapes.
The difference between the sub assembly 100a and the sub assembly 100b is that the GDL 604 comprises two planar parts 604a and 604b that are arranged face to face. The GDL parts 604a and 604b may have different porosities. The weld or projection 130 is configured to extend into both of the planar parts to hold them together with the gasket 104.
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- receiving 701 an anode flow plate 131 having the fuel cell sub assembly 100a arranged thereon;
- applying 702 a proton exchange membrane to the fuel cell sub assembly on an opposed side to the anode flow plate;
- applying 703 a further fuel cell sub-assembly to the proton exchange membrane;
- applying 704 a cathode flow plate to the further fuel cell sub-assembly on an opposed side to the proton exchange membrane.
Thus, a fuel cell may be formed comprising a proton exchange membrane, an anode plate, a cathode plate wherein the fuel cell sub assembly 100 is configured between the proton exchange membrane and one of the anode plate or cathode plate. In other embodiments, the fuel cell may include two sub-assemblies; a first sub-assembly and a second sub-assembly, the first sub-assembly between the proton exchange membrane and the anode plate and the second sub-assembly between the proton exchange membrane and the cathode plate. In some examples, the anode plate and cathode plate may comprise bipolar plates. A plurality of such fuel cells may be arranged together face to face to form a fuel cell stack.
Claims
1. A method of forming of a fuel cell sub-assembly comprising;
- placing a gasket with a peripheral seal defining a central aperture of the gasket on at least one of an anode flow plate and a cathode flow plate;
- placing a gas diffusion layer having less rigidity than the gasket within said within said central aperture; and,
- wherein the gas diffusion layer is substantially uniformly spaced by a predetermined spacing from the inside facing surface of the gasket for forming a gallery.
2. The method of fuel claim 1, wherein the gas diffusion layer is configured to substantially fill the central aperture.
3. The method of claim 1, wherein the gas diffusion layer is substantially planar.
4. The method of claim 3, wherein a gasket and gas diffusion layer are placed on each of the cathode flow plates and the anode flow plates.
5. The method of claim 4, the method further comprising adding a proton exchange membrane between the cathode flow plate and the anode flow plate.
6. A fuel cell sub-assembly comprising;
- a gasket comprising a peripheral seal for a fuel cell assembly, the peripheral seal defining a central aperture;
- a gas diffusion layer for providing diffused gases to a proton exchange membrane of a fuel cell, the gas diffusion layer located within the central aperture; and
- wherein the gasket includes a channel extending from its inside facing surface into the peripheral seal for providing a fluid connection to a fluid transfer conduit and the at least one connection point is adjacent to the channel.
7. A fuel cell sub-assembly according to claim 6, wherein the sub-assembly includes at least two distinct connection points where the gasket is in contact with the gas diffusion layer.
8. A fuel cell sub-assembly according to claim 6, wherein gas diffusion layer is substantially rectangular defined by four outwardly facing surfaces and the central aperture is substantially rectangular defined by four inwardly facing surfaces of the peripheral seal, and the or each connection point is located between a particular one of the four surfaces of the gas diffusion layer and a particular one of the four surfaces of the gasket.
9. A fuel cell sub-assembly according to claim 8, wherein the gas diffusion layer is of a porous material having spaces between gas diffusion layer material, and at the or each connection point, and the material of the gasket may be comingled with the material of the gas diffusion layer.
Type: Application
Filed: Jul 6, 2021
Publication Date: Oct 28, 2021
Applicant: Intelligent Energy Limited (Loughborough)
Inventor: Antony Richard Wilson (Loughborough)
Application Number: 17/368,785