U.S. patent application number 10/728200 was filed with the patent office on 2004-08-19 for electrochemical cell plate with integral seals.
Invention is credited to Andrews, Craig, Boyer, Chris, Fiebig, Brad, Layton, James.
Application Number | 20040159543 10/728200 |
Document ID | / |
Family ID | 32469586 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040159543 |
Kind Code |
A1 |
Boyer, Chris ; et
al. |
August 19, 2004 |
Electrochemical cell plate with integral seals
Abstract
An electrochemical cell component having a plate with opposing
faces, seal grooves formed in each of the faces, and a plurality of
holes extending through the plate between the first and second
grooves with an integral sealing member formed in the grooves and
holes. The seal grooves extend continuously around the perimeter of
the faces and the grooves may follow any type of contiguous
pattern. The component may form a frame surrounding a flow field.
Bipolar plates and fluid cooled bipolar plates may comprise this
electrochemical cell component. Alternatively, a seal groove may be
formed in only the first face and a ridge formed in the second face
of the component. The ridge may be used to form a fluid tight seal
when pressed into an opposing surface of the membrane in a membrane
and electrode assembly. A sealing material is contained within the
seal groove.
Inventors: |
Boyer, Chris; (Houston,
TX) ; Fiebig, Brad; (Bryan, TX) ; Andrews,
Craig; (College Station, TX) ; Layton, James;
(Bryan, TX) |
Correspondence
Address: |
STREETS & STEELE
13831 NORTHWEST FREEWAY
SUITE 355
HOUSTON
TX
77040
US
|
Family ID: |
32469586 |
Appl. No.: |
10/728200 |
Filed: |
December 4, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60431008 |
Dec 4, 2002 |
|
|
|
Current U.S.
Class: |
204/254 ;
204/288.1 |
Current CPC
Class: |
H01M 8/2483 20160201;
Y02E 60/50 20130101; H01M 8/0271 20130101; H01M 8/0247 20130101;
H01M 8/0267 20130101; H01M 8/242 20130101 |
Class at
Publication: |
204/254 ;
204/288.1 |
International
Class: |
C25D 017/00 |
Claims
What is claimed is:
1. An electrochemical cell component, comprising: a plate having a
first face and a second face; at least one groove formed in the
first face, the second face or a combination of the first and
second faces, wherein the at least one groove has a nonuniform
cross-section; and an integral sealing member secured in the at
least one groove, wherein the integral sealing member has a shape
that cooperates with the nonuniform cross-section of the at least
one groove to restrain removal of the sealing member.
2. The component of claim 1, wherein the integral sealing member is
formed by injection molding into the at least one groove.
3. The component of claim 1, wherein the integral sealing member is
an elastomer.
4. The component of claim 1, wherein the nonuniform cross-section
of the at least one groove includes a via extending between a
groove on the first face and a groove on the second face.
5. The component of claim 1, wherein the nonuniform cross-section
of the at least one groove includes a plurality of vias extending
between a groove on the first face and a groove on the second
face.
6. The component of claim 1, wherein the nonuniform cross-section
narrows at the surface of the plate.
7. The component of claim 1, wherein the at least one groove
extends continuously around a perimeter of the faces.
8. The component of claim 1, wherein the at least one groove has a
shape selected from circular, polygonal, irregular, and
combinations thereof.
9. The component of claim 1, wherein the at least one groove
follows a contiguous pattern over a face of the plate.
10. The component of claim 1, wherein the plate has a shape
selected from circular, ovoid, oval and elliptical.
11. The component of claim 1, wherein the plate has a shape of a
polygon.
12. The component of claim 1, wherein the plate is a frame, and
further comprising: at least one flow channel formed in the first
face of the frame from a fluid inlet manifold to an inner edge of
the frame; at least one flow channel formed in the first face of
the frame from the inner edge of the frame to a fluid outlet
manifold.
13. The component of claim 12, wherein the at least one groove
isolates each manifold from all other manifolds.
14 The component of claim 12, wherein the at least one groove
encircles all manifolds formed through the faces of the plate
except for the manifolds that are provided with the at least one
flow channel.
15. The component of claim 12, wherein the at least one groove
encircles all manifolds formed through the faces of the plate on
the second face, and wherein the grooves encircle all manifolds
formed through the faces of the plate on the first face except for
the manifolds that are provided with the at least one flow
channel.
16. The component of claim 1, wherein the plate is made of a metal
or a polymer.
17. The component of claim 1, wherein the plate is made from a
polymer selected from polyvinylidene fluoride, polyvinylidene
difluoride, polytetrafluoroethylene, polyamides, polysulfone,
polyetherketones, polycarbonate, polypropylene, polyimides,
polyurethanes, epoxies, silicones, and combinations thereof.
18. The component of claim 1, wherein the plate is formed by
injection molding.
19. The component of claim 1, wherein the plate is machined from a
solid polymer sheet.
20. The component of claim 1, wherein the plate is a frame.
21. The component of claim 20, further comprising: a flow field
disposed within the frame.
22. A bipolar plate assembly, comprising: a first and a second
frame disposed on opposite sides of a gas barrier, wherein each of
the first and second frames comprise first and second opposing
faces, a first seal groove formed in the first face, a second seal
groove formed in the second face, and a plurality of holes
extending through the frame between the first groove and the second
groove and an integral sealing member formed in the grooves and
holes.
23. The bipolar plate of claim 22, wherein the first and second
frames are bonded to the gas barrier.
24. The bipolar plate of claim 22, wherein the gas barrier is a
metal sheet.
25. The bipolar plate of claim 22, wherein the integral sealing
member is formed by injection molding.
26. The bipolar plate of claim 25, wherein the sealing member is an
elastomer.
27. The bipolar plate of claim 22, wherein the seal grooves extend
continuously around a perimeter of the faces.
28. The bipolar plate of claim 22, wherein each of the frames and
the gas barrier have a shape selected from circular, ovoid, oval,
polygonal and elliptical.
29. The bipolar plate of claim 22, further comprising: at least one
flow channel formed in the first face of the first frame from a
first fluid inlet manifold to an inner edge of the first frame; at
least one flow channel formed in the first face of the first frame
from the inner edge of the first frame to a first fluid outlet
manifold; at least one flow channel formed in the first face of the
second frame from a second fluid inlet manifold to an inner edge of
the second frame; and at least one flow channel formed in the first
face of the second frame from the inner edge of the second frame to
a second fluid outlet manifold.
30. The bipolar plate of claim 29, wherein the seal grooves on each
frame isolate each manifold from all other manifolds on each
frame.
31. The bipolar plate of claim 29, wherein the grooves encircle all
manifolds formed through the faces of each frame except for the
manifolds that are provided with the at least one flow channel.
32. The bipolar plate of claim 29, wherein the grooves encircle all
manifolds formed through the faces of each frame on the second
face, and wherein the grooves encircle all manifolds formed through
the faces of each frame on the first face except for the manifolds
that are provided with the at least one flow channel.
33. The bipolar plate of claim 22, wherein each of the frames is
made of a polymer.
34. The bipolar plate of claim 33, wherein the polymer is selected
from polyvinylidene fluoride, polyvinylidene difluoride,
polytetrafluoroethylene, polyamides, polysulfone, polyetherketones,
polycarbonate, polypropylene, polyimides, polyurethanes, epoxies,
silicones, and combinations thereof.
35. The bipolar plate of claim 33, wherein at least one of the
frames is formed by injection molding.
36. The bipolar plate of claim 33, wherein at least one of the
frames is machined from a solid block of the polymer.
37. The bipolar plate of claim 22, characterized in that the
integral seal is physically secured within the grooves.
38. The bipolar plate of claim 22, further comprising: a flow field
surrounded by one of the frames.
39. The bipolar plate of claim 38, wherein the flow field is made
of a material selected from expanded metal mesh, metal felt, metal
foam and combinations thereof.
40. A fluid cooled bipolar plate assembly, comprising: a first, a
second, and a third frame, wherein each of the frames comprise
first and second opposing faces, a first seal groove formed in the
first face, a second seal groove formed in the second face, and a
plurality of holes extending through the frame between the first
groove and the second groove and an integral sealing member formed
in the grooves and holes; a first gas barrier and a second gas
barrier, wherein the first gas barrier is disposed between the
first and second frames and the second gas barrier is disposed
between the second and third frames; a cooling flow field, wherein
the second frame surrounds the cooling flow field.
41. The fluid cooled bipolar plate of claim 40, wherein the first
and second plates are bonded to the first gas barrier and the
second and third plates are bonded to the second gas barrier.
42. The fluid cooled bipolar plate of claim 40, wherein the each of
the gas barriers is a metal sheet.
43. The fluid cooled bipolar plate of claim 40, wherein the
integral sealing member of each frame is formed by injection
molding.
44. The fluid cooled bipolar plate of claim 40, further comprising:
at least one flow channel formed in the first face of the first
frame from a first fluid inlet manifold to an inner edge of the
first frame; at least one flow channel formed in the first face of
the first frame from the inner edge of the first frame to a first
fluid outlet manifold; at least one flow channel formed in the
first face of the second frame from a second fluid inlet manifold
to an inner edge of the second frame; at least one flow channel
formed in the first face of the second frame from the inner edge of
the second frame to a second fluid outlet manifold; at least one
flow channel formed in the first face of the third frame from a
third fluid inlet manifold to an inner edge of the third frame; and
at least one flow channel formed in the first face of the third
frame from the inner edge of the third frame to a second fluid
outlet manifold.
45. The fluid cooled bipolar plate of claim 44, wherein the seal
grooves on each plate isolate each manifold from all other
manifolds on each plate.
46. The fluid cooled bipolar plate of claim 40, characterized in
that the sealing member is physically secured within the
grooves.
47. The fluid cooled bipolar plate of claim 40, further comprising:
a flow field disposed within one of the frames.
48. The fluid cooled bipolar plate of claim 40, wherein the flow
field is made of a material selected from expanded metal mesh,
metal felt, metal foam and combinations thereof.
49. An electrochemical cell, comprising: a frame having first and
second opposing faces, a seal groove formed in the first face, a
ridge formed on the second face, and a sealing member secured
within the seal groove; and a membrane compressed against the ridge
to form a seal with the second face.
50. The cell of claim 49, wherein the membrane is a part of a
membrane and electrode assembly.
51. The cell of claim 50, wherein the membrane is a proton exchange
membrane.
52. The cell of claim 49, wherein the sealing member is selected
from an o-ring and a gasket.
53. The cell of claim 49, wherein the sealing member is secured
within the seal groove by injection molding.
54. The cell of claim 49, wherein the sealing member is an
elastomer.
55. The cell of claim 49, wherein the seal groove extends
continuously around a perimeter of the first face.
56. The cell of claim 49, wherein the ridge extends around the
second face in a contiguous pattern.
57. The cell of claim 49, further comprising: at least one flow
channel formed in the first face of the plate from a fluid inlet
manifold to an inner edge of the plate; at least one flow channel
formed in the first face of the plate from the inner edge of the
plate to a fluid outlet manifold.
58. The cell of claim 57, wherein the seal groove isolates each
manifold from all other manifolds.
59. The cell of claim 57, wherein the ridge isolates each manifold
from all other manifolds.
60. The cell of claim 57, wherein the seal groove encircles all
manifolds formed through the faces of the plate except for the
manifolds that are provided with the at least one flow channel.
61. The cell of claim 57, wherein the ridge encircles all manifolds
formed through the faces of the plate except for the manifolds that
are provided with the at least one flow channel
62. The cell of claim 57, characterized in that the sealing member
is physically secured within the groove.
63. The cell of claim 57, wherein the ridge is formed in the second
face during manufacture of the plate.
64. The cell of claim 57, wherein the cell is compressed during
assembly of an electrochemical cell, and wherein the ridge is
formed by the sealing material being pushed against a floor of the
seal groove to deform the second face with the ridge.
65. The cell of claim 57, wherein the plate is a frame.
66. The cell of claim 65, further comprising: a flow field disposed
within the frame.
67. The cell of claim 66, wherein the flow field is made of a
material selected from expanded metal mesh, metal felt, metal foam
and combinations thereof.
Description
[0001] This application claims priority to U.S. Provisional Patent
Application No. 60/431,008 filed on Dec. 4, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to electrochemical cell
components that form a seal with an adjacent component, a method of
forming a seal between adjacent electrochemical cell components,
and an electrochemical cell stack that is sealed.
[0004] 2. Description of Related Art
[0005] Electrochemical cells generally employ a membrane electrode
assembly ("MEA") consisting of a solid polymer electrolyte or ion
exchange membrane disposed between two electrode layers, which are
the anode and the cathode. An electrocatalyst is disposed at each
membrane/electrode layer interface to induce the desired
electrochemical reaction. The location of the electrocatalyst
generally defines the electrochemically active area of the MEA.
[0006] In typical fuel cells, the MEA is supported on either side
by layers of screen or expanded metal (flow fields) which in turn
are surrounded by cell frames and separator plates (bipolar plates)
to form reaction chambers and to seal fluids therein. The cell
frames have at least one flow passage, and many times several flow
passages formed therein to direct the reactant fluid streams to the
respective electrode layers. For example, in a fuel cell the fuel
is directed to the anode side and the oxidant is directed to the
cathode side. In a single cell arrangement, cell frames, flow
fields and end plates are provided on each of the anode and cathode
sides of the MEA. The end plates act as current collectors and
provide support for the electrodes.
[0007] Two or more fuel cells or other types of electrochemical
cells can be connected together to form a bipolar electrochemical
cell stack. In these bipolar arrangements, one side of a given
bipolar plate communicates with an anode for one cell and the other
side of the bipolar plate communicates with the cathode for an
adjacent cell. The stack typically includes inlet ports and
manifolds for directing the reactant fluids to the anode and
cathode flow field passages respectively. The stack often also
includes an inlet port and manifold for directing a coolant fluid
to interior passages within the stack to absorb heat generated by
the exothermic reaction in the cells. The stack also generally
includes exhaust manifolds and outlet ports for expelling the
reactant fluids, any water or other products formed as a result of
the reaction, as well as an exhaust manifold and outlet port for
the coolant stream exiting the stack.
[0008] Within the stack, the individual cell frames typically
contain multiple ports for the passage of reactant fluids and
perhaps also cooling fluids. A common method for providing a fluid
communication pathway between the electrode or active area of a
cell and individual fluid manifolds in the frame comprises channels
machined into the cell frame. The channels typically comprise
grooves cut into the face of the cell frames. Fluids, after passing
through the inlet manifolds and the channels, enter the flow fields
to make contact with the electrode, and membrane. The fluids and
gas products similarly exit through opposing channels in
communication with the outlet manifolds.
[0009] Traditionally gaskets and o-rings have been used in the
assembly or electrochemical cells and cell stacks to provide the
fluid seals required to contain the fluids within various
compartments of the electrochemical cells or cell stacks. A sealing
surface is a compressible material that is placed between two
typically non-compressible surfaces to form a fluid-tight joint.
Sealing surfaces are often gaskets and o-rings that are
manufactured in a large number of sizes and shapes to provide the
compressible material required to form fluid-tight joints in a wide
variety of applications.
[0010] The cell frames are usually sealed by means of sealing
ridges that are embossed, machined, or molded into the frame. The
sealing features react against gaskets included in the stack to
maintain fluid tight joints and also grip the gaskets to prevent
creep and extrusion of the gasket. The compression of the fuel cell
stack applies the sealing force to the fluid tight resilient seals
between the various components, including frames, separator plates
and membranes. Such seals typically circumscribe the manifolds and
the electrochemically active area on the cell frame.
[0011] Another drawback of existing cell frames is the method used
to make a fluid-tight seal between the frames in a stack. Molter,
et al. discloses a typical electrochemical cell frame in U.S. Pat.
No. 6,099,716 that provides ridges on the frame's sealing surfaces
with gaskets between these surfaces. Upon assembly, Molter
discloses that the gaskets may be glued to the sealing surfaces to
keep the gaskets in place during assembly. Because of the manifolds
running through the cell frames, the gaskets are often very complex
or numerous to provide all the sealing surfaces required.
[0012] Accordingly, there remains a need for improved leak-proof
seals for use between electrochemical cell components, such as
between the frame and the bipolar plate. It would be desirable if
the seals were easier to assembly and could be integrated into
other components to reduce part count.
SUMMARY OF THE PRESENT INVENTION
[0013] The present invention provides an electrochemical cell
component having a plate with first and second opposing faces, a
first seal groove formed in the first face, a second seal groove
formed in the second face, and a plurality of holes extending
through the plate between the first groove and the second groove
and an integral sealing member formed in the grooves and holes.
Preferably, the integral sealing member is formed by injection
molding and the plate is made of a metal or polymer.
[0014] The seal grooves extend continuously around the perimeter of
the faces and the grooves may have any cross-sectional shape and
may follow any type of contiguous pattern, such as, for example, a
curvilinear path, a straight path or combinations thereof. The
plate may have any shape, including circular, ovoid, oval,
polygonal and elliptical.
[0015] There is also at least one flow channel formed in the first
face of the plate from a fluid inlet manifold to an inner edge of
the plate and at least one flow channel formed in the first face of
the plate from the inner edge of the plate to a fluid outlet
manifold. The seal grooves isolate each manifold from all other
manifolds and from leaking out of the cell.
[0016] If the plate is made of a polymer, preferred polymers
include polyvinylidene fluoride, polyvinylidene difluoride,
polytetrafluoroethylene, polyamides, polysulfone, polyetherketones,
polycarbonate, polypropylene, polyimides, polyurethanes, epoxies,
silicones, and combinations thereof. The plate may be formed, for
example, by injection molding or by being machined from a solid
block of the polymer.
[0017] A central portion of the plate may be removed, such that the
plate forms a frame that can receive other components, for example
a flow field. Alternatively, the plate may be formed as a frame
initially with a central portion sized to accommodate, for example,
a flow field or a membrane and electrode assembly. The flow field
is preferably made of a material selected from expanded metal mesh,
metal screen, metal felt, metal foam and combinations thereof.
Other electronically conductive materials may form the flow field
as well.
[0018] Additionally, the present invention provides a bipolar plate
assembly having a first and a second frame disposed on opposite
sides of a gas barrier, wherein each of the first and second frames
comprise first and second opposing faces, a first seal groove
formed in the first face, a second seal groove formed in the second
face, and a plurality of holes extending through the frame between
the first groove and the second groove and an integral sealing
member formed in the grooves and holes
[0019] Preferably, the first and second frames are bonded to the
gas barrier but they may be held in place with the compressive
forces asserted on an electrochemical stack to hold the stack
together, such as through a set of endplates. Preferably, the gas
barrier is a metal sheet or other electrically conducting
material.
[0020] The integral sealing member may be formed by injection
molding. The seal grooves extend continuously around a perimeter of
the faces, and may have any cross-sectional shape. The seal grooves
may follow a contiguous pattern, such as, for example, a
curvilinear path, a straight path or combinations thereof. The
bipolar plate may have any shape, including circular, ovoid, oval,
polygonal and elliptical.
[0021] The bipolar plate of the present invention further has at
least one flow channel formed in the first face of the first frame
from a first fluid inlet manifold to an inner edge of the first
frame, at least one flow channel formed in the first face of the
first frame from the inner edge of the first frame to a first fluid
outlet manifold, at least one flow channel formed in the first face
of the second frame from a second fluid inlet manifold to an inner
edge of the second frame, and at least one flow channel formed in
the first face of the second frame from the inner edge of the
second frame to a second fluid outlet manifold.
[0022] The seal grooves on each frame isolate each manifold from
all other manifolds on each frame. The grooves encircle all
manifolds formed through the faces of each frame except for the
manifolds that are provided with the at least one flow channel The
frames may be made of any suitable material including, for example,
metal and polymer. Acceptable polymers include polyvinylidene
fluoride, polyvinylidene difluoride, polytetrafluoroethylene,
polyamides, polysulfone, polyetherketones, polycarbonate,
polypropylene, polyimides, polyurethanes, epoxies, silicones, and
combinations thereof. The frames may be made by methods including
injection molding and being machined from a block of solid
polymer.
[0023] Flow fields are contained with in the frames. The flow
fields may be made of materials including expanded metal mesh,
metal felt, metal foam and combinations thereof.
[0024] Another embodiment of the present invention includes a fluid
cooled bipolar plate assembly having a first, a second, and a third
frame, wherein each of the frames comprise first and second
opposing faces, a first seal groove formed in the first face, a
second seal groove formed in the second face, and a plurality of
holes extending through the frame between the first groove and the
second groove and an integral sealing member formed in the grooves
and holes, a first gas barrier and a second gas barrier, wherein
the first gas barrier is disposed between the first and second
frames and the second gas barrier is disposed between the second
and third frames, and a cooling flow field, wherein the second
frame surrounds the cooling flow field.
[0025] Another embodiment of the present invention provides an
electrochemical cell component having a plate having first and
second opposing faces, a seal groove formed in the first face, a
ridge formed in the second face, and a sealing material contained
within the seal groove, wherein the second face opposes a membrane,
and wherein the ridge forms a fluid-tight seal by compressing an
opposing surface of the membrane. Bipolar plates and fluid cooled
bipolar plates may also comprise this component.
BRIEF DESCRIPTION OF THE DRAWNIGS
[0026] FIG. 1 is a top view of a frame that may be used in an
electrochemical cell or cell stack in accordance with the present
invention.
[0027] FIG. 2 is a top view of the reverse side of the frame shown
in FIG. 1.
[0028] FIGS. 3A and 3B are cross sectional side views of a
component having an integral sealing member formed in a seal
groove.
[0029] FIG. 4 is an exploded view of a bipolar plate in accordance
with the present invention.
[0030] FIG. 5 is an exploded view of a fluid cooled bipolar plate
in accordance with the present invention.
[0031] FIGS. 6A-C are cross-sectional views of an electrochemical
component having a sealing groove formed on only one face in
accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0032] The present invention provides an electrochemical cell
component having an integral sealing member. The integral sealing
member may be formed on one side or both sides of the component to
replace at least one traditional gasket or o-ring that is provided
between components during the assembly of an electrochemical cell
or stack of cells. The present invention further provides a
subassembly that includes at least one electrochemical cell
component having an integral sealing member. Further still, the
present invention provides an electrochemical cell stack including
at least one component having an integral sealing member.
[0033] In order to form an integral sealing member, a seal groove
is formed at the location where a sealing member is needed, such as
where a gasket or o-ring would traditionally have been installed
during the assembly of an electrochemical cell or cell stack. In
order to form an integral sealing member on both sides of an
electrochemical cell component, a seal groove is formed in both
faces of the component. Preferably, the seal groove on one face of
the component is in fluid communication with the seal groove on the
opposite face of the component via a plurality of vias or holes
formed approximately in the center of the seal grooves and
distributed along the length of the grooves. An integral sealing
member is then formed in the seal groove and through the holes such
that the sealing member in the groove on one face of the component
is held in place by being an integral part, through the holes, with
the sealing member in the groove on the opposite face of the
component.
[0034] An integral sealing member is preferably formed by injection
molding an elastomer into the groove or grooves provided in the
component. Suitable elastomers may be selected from a vinylidene
fluoride hexafluoro-propylene tetrafluoroethylene copolymer (such
as Viton, a trademark of DuPont), silicone, ethylene-propylene
diene elastomers (EPDM) and combinations thereof. Other suitable
materials may include elastomer grade plastics, such as olefins,
styrenes, and fluoroplastics. It should be recognized that the
sealing member will typically be over molded so that the sealing
member will extend outward beyond the surface of the component when
the sealing member is not being compressed. The over molded portion
of the sealing member may have any shape as determined by the
invention mold, but may include, without limitation, rectangular,
semicircular, triangular, and ribbed.
[0035] The overall shape of the components provided by the present
invention are not limited but rather may take any shape required by
the configuration of a particular electrochemical cell or cell
stack. Normally the component will be substantially planar in one
dimension and have a curvilinear shape in the other two dimensions,
such as a plate, but the shape of the planar component may include,
without limitation, circular, ovoid, oval, elliptical and
polygonal.
[0036] The groove itself may have any cross-sectional shape
including, without limitation, rectangular, semicircular, arches,
triangular, other polygon, and irregular shape. Preferably, the
groove is designed in a manner that the sealing member formed
within the groove will be partially or completely physically
restrained within the groove to prevent accidental displacement or
improper positioning of the sealing member. By restraining the
sealing member within the groove, the component becomes an
integrated component. In embodiments that include a single groove,
i.e., the component does not include an opposing groove with vias
therebetween, it is preferred for the cross-sectional shape of the
groove to be wider at depth within the component than at the rim of
the groove so that the sealing member formed within the groove will
become physically restrained. In embodiments that have opposing
grooves connected by vias, the sealing member is formed through the
via and into the grooves and becomes restrained in position in that
manner regardless of whether the cross-sectional shape of the
groove is itself restraining. It should also be recognized that the
sealing member may be restrained within the groove by adhesive
bonding.
[0037] The component will have a groove that may follow a simple or
complex continuous path or the component will have a plurality of
grooves that may follow discontinuous paths. It is preferable that
all the grooves be in fluid communication so that a single
injection molding step can form the sealing member or members. This
fluid communication can be provided by having a continuous groove,
by providing vias between grooves, or by providing an injection
mold that allows fluid communication therebetween. It should be
recognized that grooves on opposing sides of the component may be
the same or different. Furthermore, grooves on opposing sides may
be restrained through the use of vias, through the use of inward
widening cross-sectional shapes, or a combination thereof.
[0038] A conventional electrochemical cell stack comprises a
plurality of membrane and electrode assemblies (MEA) that are each
disposed between two flow fields to form one electrochemical cell,
with each of these electrochemical cells separated by a bipolar
plate. The flow fields ensure that the reactant fluids are well
distributed across the face of the electrodes and they also act as
electrical current collectors, transmitting electrons from the
anode of a first cell to a bipolar plate and from the bipolar plate
to the cathode of an adjacent cell. The flow fields are surrounded
by frames. The MEAs are securely positioned between the flow
fields. Reactant fluids are provided to the flow fields through
manifolds that are formed in the manifold region of any component
that extends into the manifold region, such as the frames, MEAs and
bipolar plates. Flow channels are provided in the frames to direct
the reactant fluids from an inlet manifold in the frame, across the
flow field to an outlet manifold in the frame. Preferably, the
sealing surfaces between the frames and bipolar plates in the stack
are arranged to provide fluid tight seals around the perimeters of
the frames and bipolar plates and also around each individual fluid
manifold in the frames and bipolar plates. While less preferred, it
is also possible to incorporate the present invention into a
component for an internally manifolded electrochemical cell.
[0039] One embodiment of the present invention is a frame for use
in an electrochemical cell or cell stack. The frame may be made of
any material, including metal, but is preferably an electrically
nonconducting material, such as a polymer. Examples of polymers
that are suitable for making an electrochemical cell plate include
polyvinylidene fluoride, polyvinylidene difluoride,
polytetrafluoroethylene, polyamides, polysulfone, polyetherketones,
polycarbonate, polypropylene, polyimides, polyurethanes, epoxies,
silicones, and combinations thereof. Frames made of polymer may be
formed by injection molding or by machining the frame from a solid
block of the polymer.
[0040] The frame is provided with inlet and outlet manifold holes
for each of the fluids provided to the electrochemical cell stack.
These fluids include the anodic reactant fluid, the cathodic
reactant fluid and cooling or heating fluids, if required by the
stack. The frame may surround other components of the
electrochemical cell or stack such as a flow field or an MEA. One
or more flow channels are formed in a first face of the frame from
an inlet manifold to the inner edge of the frame. One or more flow
channels are also formed in the same face from the inner edge of
the frame to an outlet manifold. The flow channels allow a fluid to
circulate from an inlet manifold to the flow field and from the
flow field to an outlet manifold. If the fluid is totally consumed
flowing across the electrode, an outlet manifold may not be
required. It should be recognized that the sealing grooves should
not interfere with the flow channels. While less preferred, the
flow channels can also be provided as holes passing within the
plane of the component from the manifold to the flowfield.
[0041] The second face or side of the frame may include flow
channels, but in order to protect the delicate membrane of the MEA,
the flow channels are preferably only provided in the face of the
frame that faces the bipolar plate. Otherwise the sharp edges of
the flow channels or the flow of the fluid through the channels to
the flow fields may damage the delicate membrane secured between
opposing frames in an electrochemical cell.
[0042] The integral sealing member will normally extend around the
entire circumference of the frame to seal the fluids into the
electrochemical cell or cell stack. The integral sealing member
will normally also extend around each of the manifold holes to
provide a fluid tight seal that contains the fluids flowing through
the manifolds. The sealing member will not extend totally around
the manifolds that are open to a particular flow field through flow
channels so that the fluid may flow between those particular
manifolds and the flow field. Since the flow channels are
preferably only formed on the face of the frame facing the bipolar
plate, it is an option for the sealing member to totally encircle
the manifold on the face without the flow channels.
[0043] The flow field may be bonded to the frame or the flow field
may simply fit within the frame so that the flow field is
surrounded by the frame but not bonded to the frame. The flow field
may be made of a material selected from expanded metal mesh, metal
felt, metal foam and combinations thereof.
[0044] The present invention also provides a bipolar plate for use
in an electrochemical cell stack. The bipolar plate assembly
comprises a first and second plate, as described above, disposed on
opposite sides of a gas barrier. Optionally, the first and second
frames may be bonded to the gas barrier to facilitate assembly of
the electrochemical cell stack. The gas barrier is typically a
metal sheet, but may also include a composite material providing
water transport to the anode or cathode. Other materials known to
those skilled in the art may be used to form the gas barrier as
long as the materials are electrically conductive or an alternative
electrical conductor is provided between cells.
[0045] The present invention further provides a fluid cooled
bipolar plate for use in an electrochemical cell stack. The fluid
cooled bipolar plate comprises first, second and third frames as
described above, where the first and second frames are disposed on
opposite sides of a first gas barrier and the second and third
frames are disposed on opposite sides of a second gas barrier. The
second frame surrounds a flow field for a cooling fluid. The
cooling fluid circulates through the flow field from a cooling
fluid supply manifold to a cooling fluid return manifold similar to
the reactant fluid flow described above. Alternatively, the fluid
cooled bipolar plate may be used as a fluid heating bipolar plate
if a heating fluid is circulated through the flow field rather than
a cooling fluid.
[0046] Another embodiment of the present invention forms a sealing
member on only one face of the electrochemical cell component. When
assembling electrochemical cell stacks, membrane and electrode
assemblies (MEA) are sandwiched between other components. The
membrane itself may extend into the sealing areas of the
electrochemical stack and act as a gasket or sealing member. The
membrane of the MEA is a compressible material and therefore, when
compressed between two rigid surfaces, the membrane creates a fluid
tight seal. Therefore, if there is an MEA on one side of a
component, such as a frame surrounding a flow field or a bipolar
plate, the side of the frame or bipolar plate facing the MEA does
not require an additional sealing member in order to form a fluid
tight seal, because the membrane can serve that function. Membranes
are conventionally made of perfluorosulfonic acids (PFSA) or other
membranes known to those having ordinary skill in the art.
[0047] In designing electrochemical cell stacks that operate at
high pressures, it is preferable to apply high localized
compression of the sealing member rather than a lower compression
across a larger interfacial area. Accordingly, the sealing members
of the invention are preferably narrow and consume less than 20
percent of the face of the component. Where the sealing member is
disposed over more than 20 percent of the facial area of a
component, such as where the membrane extends between two
components, then it is preferred to provide a ridge on the face of
the component that pushes into the sealing member to form a fluid
tight seal. The ridge pushes into the sealing member and forms a
narrow but very fluid tight and pressure resistant seal. The ridge
may be machined into the component face facing the membrane, or it
may be formed in the frame if the frame is made in a mold, as by
injection molding. Alternatively, the portion of the component
underlying the seal groove may be made to bow outwardly and form a
ridge under the force of the over-molded sealing member being
compressed into the seal groove during assembly. If the component's
thickness around the seal groove is sufficiently thin, compression
of the component during assembly creates a ridge from the sealing
material pushing against the floor of the seal groove.
[0048] An advantage of using this embodiment in assembling an
electrochemical cell stack is that there is a reduction in the
total number of parts required to assemble the electrochemical cell
stack. Additionally, the total weight of the electrochemical cell
stack is less using this embodiment because the weight of further
o-rings, gaskets or other sealing materials no longer contributes
to the overall weight of the electrochemical cell stack.
Furthermore, by removing these o-rings, gaskets or other sealing
materials, the overall size, especially thickness, of the
electrochemical cell stack is likewise reduced, resulting in a
smaller electrochemical cell stack.
[0049] FIG. 1 is a top view of a preferred frame assembly that may
be used in an electrochemical cell or cell stack in accordance with
the present invention. The frame assembly is shown as circular,
though any shape required by a particular electrochemical cell or
cell stack would be satisfactory.
[0050] The frame 11 surrounds a flow field 14. Fluid flowing
through the inlet manifold 18 enters the flow channels 15 formed in
the face of the frame 11. The flow channels 15 direct the fluid to
the inner edge 20 of the frame and into the flow field 14. The
fluid flows across the flow field 14 and then to the flow channels
15 formed in the face of the frame 11 at the outlet manifold 19.
Other manifolds are also formed in the frame 11. These manifolds
include two other inlet manifolds 16, 22 and two other outlet
manifolds 17, 21. These manifolds are not in fluid communication
with the flow field 14 but are in fluid communication with other
flow fields contained within the electrochemical cell stack. With
three sets of manifolds, this type of frame may supply, for
example, an anode reactant fluid to an anode flow field, a cathode
reactant fluid to a cathode flow field and a cooling fluid to a
cooling fluid flow field to form a fluid cooled bipolar plate.
Fewer or more manifolds may be provided in the frames as required
by a particular application.
[0051] A seal groove 13 is formed in the face around the
circumference of the frame 11. The seal groove 13 is formed
wherever a sealing surface is required to seal the fluids within
the electrochemical cell or cell stack. The seal groove 13 also
totally surrounds each of the manifolds 16, 17, 21, 22 that are not
in fluid communication with the flow field 14. The seal groove 13
does not totally surround the manifolds 18, 19 that are in fluid
communication with the flow field 14, but only surrounds that
portion of the manifolds 18, 19 that must have a fluid tight seal
to prevent the fluids from leaking from the electrochemical cell or
cell stack.
[0052] FIG. 2 is a top view of the reverse side of the frame shown
in FIG. 1. The seal groove 13 is formed in the reverse side of the
frame 11 at the same location as on the front side of the frame 11
as shown in FIG. 1. As on the front side of the frame 11, the seal
groove 13 is formed wherever a sealing surface is required to seal
the fluids within the electrochemical cell or cell stack. As on the
front side of the frame 11, the seal groove does not totally
surround the inlet and outlet manifolds 18, 19 that are in fluid
communication with the flow field 14. Alternatively, the seal
groove may totally surround these manifolds 18, 19 on the reverse
side of the frame 11, if desired, because the fluid flow is
directed through the flow channels 15 on the front side of the
frame 11 as shown in FIG. 1. Alternatively, flow channels may also
be provided, if desired, on the reverse side of the frame 11 for
some or all manifolds in fluid communication with the flow field
14.
[0053] A plurality of holes 12 are formed through the frame 11 in
the seal groove 13, preferably near the center of the groove. These
holes 12 allow a sealing material that fills the seal grooves 13 to
connect with and hold in place the sealing surfaces on each side of
the frame 11. These sealing surfaces are thus an integral sealing
member that is formed in the seal grooves 13 and holes 12 formed in
the frame 11.
[0054] FIG. 3A is a cross sectional side view showing the integral
sealing member 25 formed in the seal groove 13 of the frame 11
shown in FIGS. 1 and 2. The material forming the integral sealing
member may be an elastomer or other suitable polymer and is
preferably formed in the seal grooves 13 by injection molding. FIG.
3B is a cross-sectional side view of integral sealing members 26
formed on a single face of a component.
[0055] FIG. 4 is an exploded view of a bipolar plate in accordance
with the present invention. The bipolar plate assembly 30 comprises
two frames 11 disposed on opposite sides of a gas barrier 31. The
frames 11 may be bonded to the gas barrier 31 using adhesives, heat
bonding or other means know to those skilled in the art or the
frames may be compressed against the gas barrier without bonding.
If the frames are bonded to the gas barrier, assembly of an
electrochemical stack may be facilitated. The frames 11 are as
described in FIGS. 1 and 2. The flow fields 14 are surrounded by
the frames 11.
[0056] One side of the bipolar plate assembly 30 is the anode side
32 and the other side of the bipolar plate assembly 30 is the
cathode side 33. The supply manifold 16 on the anode side 32 is
provided with flow channels 15 on the side facing the gas barrier
31. Likewise, it may be seen that there are no flow channels on the
inlet manifold 18 on the cathode side 33, since this figure shows
the side of the cathode frame 11 facing away from the gas barrier
30. Flow fields 14 are provided and are surrounded by the frames
11. The flow fields 14 may be of different material and different
construction from each other depending on the particular
application. Furthermore, the flow fields may be used in
communication with gas diffusion layers, current collector grids,
and the like.
[0057] The integral sealing member 25 forms a fluid tight seal
between the frames 11 and the gas barrier 31. It may be noted that
there is no seal totally surrounding the supply manifold 18 in the
frame 11 on the cathode side 33. Alternatively, a sealing member
may be formed around this manifold 18 on the side of the frame 11
facing away from the gas barrier 31.
[0058] FIG. 5 is an exploded view of a fluid cooled bipolar plate
in accordance with the present invention. The fluid cooled bipolar
plate 40 comprises a flow field 41 that is provided with a cooling
fluid circulating through the flow field 41 via a set of manifolds
22. The cooling flow field 41 is disposed between two gas barriers
31 forming the cooling section 42 of the fluid cooled bipolar plate
40. The anode side 32 is on one side of the cooling section 42 and
the cathode side 33 is on the other side of the cooling section 42.
It should be noted that a heating fluid may be substituted for the
cooling fluid circulating through the cooling flow field 41 to add
heat to the electrochemical cell if necessary.
[0059] FIGS. 6A-C are cross-sectional views of a component that
forms a ridge on one face due to the compression of a sealing
member in a sealing groove formed on the other face. In FIG. 6A, a
component 60 has a seal groove 61 formed in the first face 65 of
the component 60. A sealing member 62 is contained within the seal
groove 61. In FIG. 6B, the sealing member 62 is compressed, during
assembly of the electrochemical cell stack, creating a ridge 63 in
the second face 66 of the component 60. The ridge 63 forms a fluid
tight seal by compressing the membrane (not shown) of a MEA during
assembly. In FIG. 6C, an alternative component is shown having a
ridge 64 permanently formed in the second face 66 of the component
60 during manufacturing of the component. The ridge 64 forms a
fluid tight seal by compressing the membrane (not shown) of a MEA
during assembly. It should be recognized that the permanent ridge
does not have to directly oppose the seal groove and that any
number, size or shape of ridges may be provided.
[0060] It will be understood from the foregoing description that
various modifications and changes may be made in the preferred
embodiment of the present invention without departing from its true
spirit. It is intended that this description is for purposes of
illustration only and should not be construed in a limiting sense.
Only the language of the following claims should limit the scope of
this invention.
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