U.S. patent application number 10/554515 was filed with the patent office on 2006-09-28 for bipolar plate comprising metal wire.
Invention is credited to Lieven Anaf.
Application Number | 20060213767 10/554515 |
Document ID | / |
Family ID | 33395702 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060213767 |
Kind Code |
A1 |
Anaf; Lieven |
September 28, 2006 |
Bipolar plate comprising metal wire
Abstract
A bipolar plate as subject of the invention comprises a polymer
wall (420) and a first (430) and a second (440) electrode. The
first electrode is positioned at a first side of the polymer wall
and the second electrode is positioned at the second side of the
polymer wall. The first and the second electrode are partially
embedded in the polymer wall where they make electrical contact
with each other in the polymer wall. At least one of the electrodes
comprises a metal wire knitted fabric, which is partially embedded
in the polymer wall.
Inventors: |
Anaf; Lieven; (Waregem,
BE) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Family ID: |
33395702 |
Appl. No.: |
10/554515 |
Filed: |
April 29, 2003 |
PCT Filed: |
April 29, 2003 |
PCT NO: |
PCT/EP03/50130 |
371 Date: |
October 26, 2005 |
Current U.S.
Class: |
204/268 |
Current CPC
Class: |
C25B 9/65 20210101; H01M
8/0221 20130101; H01M 4/8605 20130101; Y02E 60/50 20130101; Y02E
60/36 20130101 |
Class at
Publication: |
204/268 |
International
Class: |
C25B 9/08 20060101
C25B009/08 |
Claims
1. A bipolar plate comprising a polymer wall which comprises a
first side and a second side, said plate further comprising a first
and a second electrode, said first electrode positioned at said
first side of said polymer wall, said second electrode positioned
at said second side of said polymer wall, said first and said
second electrode being partially embedded in said polymer wall,
said first and said second electrode making electrical contact with
each other in said polymer wall, characterized in that at least one
of said first or second electrode comprises a metal wire knitted
fabric, being partially embedded in said polymer wall.
2. A bipolar plate as in claim 1, wherein said first and said
second electrode comprise a metal wire knitted fabric being
partially embedded in said polymer wall.
3. A bipolar plate as in claim 1, wherein said electrodes consist
of metal wire knitted fabrics.
4. A bipolar plate as in claim 1, wherein said first and said
second electrode comprise more than one layer of wire knitted
fabric, only one of said layers of metal wire knitted fabric of
each of said electrodes being partially embedded in said polymer
wall.
5. A bipolar plate as in claim 1, wherein said metal wire knitted
fabric has a density of less than 10%.
6. A bipolar plate as in claim 1, wherein said polymer wall is a
polymer sheet.
7. A bipolar plate as in claim 6, wherein said polymer sheet is an
extruded polymer sheet.
8. A bipolar plate as in claim 1, wherein said metal wire knitted
fabric is provided using Ni or Ni-alloy metal wire.
9. A bipolar plate as in claim 1, wherein said metal wire knitted
fabric comprises metal wire having a diameter of less than 0.5
mm
10. A bipolar plate as in claim 1, wherein said polymer wall is
provided using a polymer material selected from the group
consisting of fluoro-polymers, polyolefines, or polyacetal or
polysulfon.
11. A bipolar plate as in claim 1, wherein said polymer wall has a
thickness of more than 0.5 mm, said polymer wall having a thickness
of less than 5 mm.
12. A bipolar plate as in claim 1, wherein said first and said
second electrode each has a thickness of more than half of the
thickness of said polymer wall.
13. A bipolar plate as in claim 1, wherein said first electrode
and/or said second comprises a catalyst.
14. A bipolar plate as in claim 1, wherein said first and/or said
second electrode comprises a catalyst selected from the group
consisting of Rh, Ru, Pt, Pd, Ir, Ag, Ni, Cu, WC or Au or
combinations thereof.
15. A method to provide a bipolar plate, said method comprising the
steps of Providing a polymer wall; Providing a first electrode
comprising a metal wire knitted fabric; Providing a second
electrode comprising a metal wire knitted fabric; Providing said
first electrode at a first side of said polymer wall; Providing
said second electrode at a second side of said polymer wall;
Laminating said first and said second electrode and said polymer
wall.
16. The use of a bipolar plate as in claim 1 in electrochemical
reactors.
17. The use of a bipolar plate as in claim 1 for production of
H.sub.2.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to bipolar plates, especially
for use in electrochemical processes. The present invention also
relates to methods for providing such bipolar plates
BACKGROUND OF THE INVENTION
[0002] Bipolar plates are well known for use in electrochemical
processes, e.g. full cells. Reactors of electrochemical processes
may comprise an anode and a cathode chamber being separated from
each other by means of a liquid and gas tight barrier. Meanwhile,
an electrically conductive electrode is provided in this anode and
cathode chamber.
[0003] The bipolar plate may act as a liquid and gas barrier
between anode and cathode chamber.
[0004] In some cases, the electrodes from the anode side and the
cathode side are to be in electrical contact with each other.
EP229473B1 describes such a bipolar plate comprising a polymer wall
and a first and a second electrode, each at one side of the polymer
wall. The electrodes are provided using an undulated, possibly
perforated metal sheet or an undulated wire mesh, in the form of a
woven structure. The electrodes are partially embedded in the
polymer wall, and make electrical contact with each other in the
polymer wall.
[0005] The stiffness of the perforated metal plate, and the
relative large amount of metal to be anchored in the polymer wall,
renders the embedding of the electrodes in the polymer wall
relatively difficult, causing uncertainty with regard to the
necessary contact of both electrodes in the polymer wall. The
presence of such amount of metal sheet causes significant pressure
drops necessary for evacuation of distribution of reactant gasses
in the electrodes. It also causes the bipolar plate to have a
relatively large weight.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a
bipolar plate, which is an alternative for the bipolar plates
presently known in the art. It is also an object of the present
invention to facilitate the embedding of the electrodes in the
polymer wall. It is also an object of the present invention to
provide a bipolar plate having an improved anchoring of the
electrode to the polymer wall. It is also an object of the present
invention to provide a bipolar plate having a more certain contact
of both electrodes in the polymer wall. It is further an object of
the present invention to provide a bipolar plate improving the
evacuation of gasses obtained as a result of the electrochemical
reactions. It is also an object of the present invention to
facilitate the distribution of gasses being reactants for the
electrochemical reactions over the whole surface of the electrodes.
It is an other object of the present invention to obtain a bipolar
plate with improved distribution of liquids used for the
electrochemical reaction. It is still an other object of the
present invention to provide a bipolar plate with reduced weight.
It is further an object of the present invention to provide a
bipolar plate, which is less expensive to produce.
[0007] A bipolar plate as subject of the invention comprises a
polymer wall and a first and a second electrode. The first
electrode is positioned at a first side of the polymer wall,
whereas the second electrode is positioned at the second side of
the polymer wall. Both electrodes are partially embedded in the
polymer wall, making electrical contact with each other in this
polymer wall. The bipolar plate as subject of the invention is
characterized in that at least one of the first or second
electrodes comprises a metal wire knitted fabric, which is
partially embedded in the polymer wall. Possibly both electrodes
comprise metal wire knitted fabrics, which are partially embedded
in the polymer wall. The electrodes may even consist of metal wire
knitted fabric. Possibly each electrode comprises more than one
layer of metal wire knitted fabric, all layers added one on top of
the other. The layer closest to the polymer wall is partially
embedded in the polymer wall.
[0008] It was also found that the use of metal wire knitted
fabrics, the embedding of the fabrics is facilitated and can be
done in a more accurate way. It was also found that the use of a
metal wire knitted fabric, who is partially embedded in the polymer
wall, provides an improved anchoring of the electrode in the
polymer wall. As both electrodes are partially embedded in the
polymer wall and make electrical contact in the polymer wall, the
improved anchoring results in a more certain electrical contact
between the electrodes over time.
[0009] It was found that when bipolar plates as subject of the
invention, comprising electrodes consisting of possibly more than
one layer of metal wire knitted fabric for each electrode, are used
in electrochemical processes, the gasses obtained by the chemical
reactions may more easily and with less pressure drop be evacuated
from the electrodes.
[0010] Also, it was found that in case gasses are used as
reactants, such gasses are distributed more easily and equally over
the whole electrode volume, requiring less pressure to be
distributed. It was further found that liquids used during
electrochemical reaction are distributed more easily and equally
over the whole electrode volume. As less metal volume is necessary
to provide the electrodes as compared with undulated sheets or
alike, the bipolar plate is less heavy. The fact of comprising less
metal volume may also decrease the production price of bipolar
plates.
[0011] The metal wire knitted product, used to provide a bipolar
plate as subject of the invention, is not necessarily to be
undulated as for the bipolar plates of the prior art. Therefor one
step in production of bipolar plates may be avoided, further
reducing production costs.
[0012] Metal wire having a diameter in the range of 0.05 mm to 0.5
mm may be used to provide the metal wire knitted fabrics. More
preferred, metal wires with a diameter in the range of 0.05 mm to
0.3 mm, such as in the range of 0.05 mm to 0.25 mm or in the range
of 0.05 mm to 0.1 mm may be used. As metal wire, metal wires out of
Ni or Ni-alloy may be used. Alternatively titanium, titanium
alloys, or stainless steel alloys, such as alloys of the AISI
300-series or AISI 400-series may be used, e.g. AISI 302, AISI 304,
AISI 310, AISI 316, AISI 316L, AISI 347, AISI 430, AISI 434 or AISI
444.
[0013] The polymer wall preferably is a polymer sheet. The
thickness of the polymer wall is preferably more than 0.5 mm but
less than 5 mm. The selection of the thickness may influence the
gas and liquid impermeability of the polymer wall, and may
influence the diffusion coefficient of gas molecules through the
polymer wall.
[0014] As polymer wall, the polymer material used to provide the
polymer wall is preferably selected from the group consisting of
fluoro-polymers such as polytetrafluorethylene, or polyolefines,
such as e.g. polypropylene, polyethylene or high-density
polyethylene, polyacetal or polysulfon. Most preferred, the polymer
wall is a polymer sheet, being obtained by extrusion processes.
Extruded polymer sheets guarantee to a larger extent the gas- and
liquid-tightness.
[0015] The two electrodes, of which at least one comprises a metal
wire knitted fabric, are embedded partially in the polymer wall.
Most preferred, the metal wire knitted fabrics are laminated
together with the polymer wall, which is preferably a polymer
sheet. The depth of the embedding of one of the metal wire knitted
fabrics of the electrodes is chosen in such a way that both
electrodes contact each other in the polymer wall, so providing
electrical contact between the two electrodes.
[0016] In order to have still a part of the metal wire knitted
fabric not embedded at both sides of the polymer wall, the
thickness of the metal wire knitted fabric being more than half of
the thickness of the polymer wall. Preferably, the metal wire
knitted fabric has a thickness less than 5 mm.
[0017] The density of the metal wire knitted fabric is preferably
less than 10%.
[0018] The electrode may comprise additional elements next to the
partially embedded metal wire knitted fabric, e.g. spacing elements
or catalyst carrying elements. Possibly more than one layer of
metal wire knitted fabric may be used for each electrode, one layer
being on top of the other, as an example to provide sufficient
volume to the electrode or to provide the other elements of the
electrode.
[0019] On one or both electrodes, a catalyst for use in the
electrochemical reaction may be present. E.g. a catalyst selected
from the group consisting of Rh, Ru, Pt, Pd, Ir, Ag, Ni, Cu, WC or
AU or combinations thereof may be used. The catalyst on the first
electrode may be identical or different as the catalyst on the
second electrode.
[0020] Possibly, the catalysts are only present at a certain zone
of the electrode. As an example, the catalyst may only be present
at the side of the electrode removed from the polymer wall.
[0021] As an example, an electrode may comprise a first metal wire
knitted fabric, partially embedded in the polymer wall as subject
of the invention. A second metal wire knitted fabric functioning as
spacing layer between the first metal wire knitted fabric and the
catalyst carrier is present on top of the first metal wire knitted
fabric. On top of the second metal wire knitted fabric, a third
metal fiber knitted fabric being coated with a catalyst, is
provided functioning as catalyst carrier.
[0022] The bipolar plates as subject of the invention may be used
in all kinds of electrochemical reactors, such as e.g. fuel cells,
electrolysers or H.sub.2-production units.
[0023] In case the electrode comprises more than one layer of metal
wire knitted fabric, only some layers may be coated with a
catalyst. Most preferred, the metal wire knitted fabric who is
partially embedded in the polymer wall is not coated with a
catalyst.
[0024] It is further an object to provide a method of providing a
bipolar plate, comprising the steps of [0025] Providing a polymer
wall; [0026] Providing a first electrode comprising a metal wire
knitted fabric; [0027] Providing a second electrode comprising a
metal wire knitted fabric; [0028] Providing the first electrode at
a first side of the polymer wall; [0029] Providing the second
electrode at a second the of said polymer wall; [0030] Laminating
the first and said second electrode and the polymer wall.
[0031] The method provided bipolar plates in a more economic way,
and in the mean time it is easy to control, as some process
parameters, e.g. pressure during lamination is less critical. The
latter is due to the elasticity the metal wire knitted fabrics
possess in a direction perpendicular to its surface.
[0032] Possibly the method of production of a bipolar plate as
subject of the invention further comprises the step of coating one
or both of the metal wire knitted fabrics with a catalyst.
[0033] Possibly the method of production of a bipolar plate further
comprises the step of adding different layers of metal wire knitted
fabric one on top of the other before or after laminating, in order
to obtain electrodes comprising more than one layer of metal wire
knitted fabric.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] The invention will now be described into more detail with
reference to the accompanying drawings wherein
[0035] FIG. 1 shows schematically a side view of a bipolar plate as
subject of the invention;
[0036] FIG. 2 shows schematically a cross section according to
plane AA' of a bipolar plate as subject of the invention of FIG.
1.
[0037] FIG. 3 and FIG. 4 show schematically a cross section of
alternative bipolar plates as subject of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0038] A side view of a bipolar plate 110 as subject of the
invention is shown in FIG. 1. A polymer wall 120 has two outer
surfaces, and at least in one surface 121, a metal wire knitted
fabric 130 being part of an electrode is partially embedded in the
polymer wall 120. At the other side 122 of the polymer wall 120,
possibly another metal wire knitted fabric 140 (not shown for
reason of clarity in FIG. 1) being part of the electrode at the
other side 122 is partially embedded in the polymer wall 120.
[0039] FIG. 2 shows a cross section of the bipolar plate 110,
having two electrodes comprising metal wire knitted fabric (130 and
140), one at each side of the polymer wall 120.
[0040] A bipolar plate 110 comprises a polymer wall 120 with a
thickness 221, e.g. 2 mm. At both sides 121 and 122 of the polymer
wall 120, preferably an extruded HDPP, HDPE, polysulfon or
polyacetal sheet, a metal wire knitted fabric 130 and 140 is
partially embedded over a depth of slightly more than half of the
thickness 221 of the polymer wall 120. It is understood that the
thickness 233 and 243 of the metal wire knitted fabrics is to be
substantially more than this half of the thickness 221 of the
polymer wall 120, in order to provide a significant volume to the
electrode which is not embedded in the polymer wall, providing void
volume to the electrodes for gas evacuation of supply of reactant
gas or reactant liquid.
[0041] Possibly, the metal wire knitted fabric 130 may be coated
with a catalyst based on Pt and Ru. The metal wire knitted fabric
140 may be coated with a catalyst based on Pt and Ir.
[0042] The metal wire knitted fabrics 130 and 140 may be a double
bed knitted structure (either warp of weft knitted) using a machine
gauge of 5 (5 needles per inch of needle bed). A nickel wire of
diameter 250 .mu.m may be used.
[0043] The metal wire knitted fabric is preferably embedded in the
polymer wall, being preferably a polymer sheet, by laminating the
knitted fabric in the sheet.
[0044] A cross section of an alternative bipolar plate as subject
of the invention is shown in FIG. 3.
[0045] The bipolar plate 310 comprises a polymer wall 320, being an
extruded polymer sheet of high-density polypropylene (HDPP),
polysulfon, polyacetal or high-density polyethylene (HDPE). The
thickness 321 of the polymer sheet is approximately 1 mm. At one
side of the polymer wall 311, a first electrode 330 is located,
comprising two layers of metal wire knitted fabric (indicated 331
and 332), the layer of metal wire knitted fabric 331, closest to
the polymer wall 320 is partially embedded in the polymer wall 320.
The thickness of the electrode (indicated 333), being the sum of
thickness of layer 331 and layer 332, is approximately 7 mm,
wherein each layer 331 and 332 has a thickness of approximately 3.5
mm.
[0046] Layer 331 is embedded in polymer wall over a depth of
slightly more than 0.5 mm.
[0047] At the other side 312 of the polymer wall, a second
electrode 340 is located, comprising two layers of metal wire
knitted fabric (indicated 341 and 342), the layer of metal wire
knitted fabric 341, closest to the polymer wall 320 is partially
embedded in the polymer wall 320. The thickness of the electrode
(indicated 343), being the sum of thickness of layer 341 and layer
342, is approximately 7 mm, wherein each layer 341 and 342 has a
thickness of approximately 3.5 mm.
[0048] Layer 341 is embedded in polymer wall over a depth of
slightly more than 0.5 mm.
[0049] As both metal wire knitted products 331 and 341 are embedded
using a depth of slightly more than half of the thickness 321 of
the polymer wall, an electrical contact between both metal wire
knitted fabrics 331 and 341, and thus between both electrodes 330
and 340 is ensured.
[0050] As an example, the metal wire knitted fabrics 331, 332, 341,
and 341 may be a single jersey knitted structure using a machine
gauge of 5 (5 needles per inch of needle bed). A nickel wire of
diameter 250 .mu.m may be used, providing a metal wire knitted
fabric having a thickness of approximately 3.5 mm, having a weight
of 47.5 g/m.sup.2 and density of 1.7%
[0051] Possibly, the layer 332 may be coated with a catalyst based
on Pt and In. The layer 342 may be coated with a catalyst based on
Pt and Ir.
[0052] A cross section of an alternative bipolar plate as subject
of the invention is shown in FIG. 4.
[0053] The bipolar plate 410 comprises a polymer wall 420, being an
extruded polymer sheet of high-density polypropylene (HDPP),
polysulfon, polyacetal or high-density polyethylene (HDPE). The
thickness 421 of the polymer sheet is approximately 1 mm. At one
side of the polymer wall 411, a first electrode 430 is located,
comprising three layers of metal wire knitted fabric (indicated
431, 432 and 433), the layer of metal wire knitted fabric 431,
closest to the polymer wall 420 is partially embedded in the
polymer wall 420. The thickness of the electrode (indicated 434),
being the sum of thickness of layer 431, layer 432 and layer 433,
is approximately 10.5 mm, wherein each layer 431, 432 and 433 has a
thickness of approximately 3.5 mm.
[0054] Layer 431 is embedded in polymer wall over a depth of
slightly more than 0.5 mm.
[0055] At the other side 412 of the polymer wall, a second
electrode 440 is located, comprising three layers of metal wire
knitted fabric (indicated 441, 442 and 443), the layer of metal
wire knitted fabric 441, closest to the polymer wall 420 is
partially embedded in the polymer wall 420. The thickness of the
electrode (indicated 444), being the sum of thickness of layers
441, 442 and 443, is approximately 10.5 mm, wherein each layer 341
and 342 has a thickness of approximately 3.5 mm.
[0056] Layer 441 is embedded in polymer wall over a depth of
slightly more than 0.5 mm.
[0057] As both metal wire knitted products 431 and 441 are embedded
using a depth of slightly more than half of the thickness 421 of
the polymer wall, an electrical contact between both metal wire
knitted fabrics 431 and 441, and thus between both electrodes 430
and 440 is ensured.
[0058] The metal wire knitted fabrics 441, 442, 443, 431, 432 and
433, may be identical as the metal wire knitted fabric used for the
embodiment as shown in FIG. 3.
[0059] The metal wire knitted fabrics 432 and 442 function as
spacing layers between the first metal wire knitted fabrics 431 and
441, and the third metal wire knitted fabrics 433 and 443, which
are coated with a catalyst based on Pt and In for metal wire
knitted fabric 433 and a catalyst based on Pt and Ir for metal wire
knitted fabric 443.
* * * * *