U.S. patent application number 14/956864 was filed with the patent office on 2016-03-31 for fuel cell and method for the production thereof.
This patent application is currently assigned to PLANSEE SE. The applicant listed for this patent is Plansee SE. Invention is credited to Marco Brandner, Thomas Franco, Georg Kunschert, Reinhold Zach, Gebhard Zobl.
Application Number | 20160093900 14/956864 |
Document ID | / |
Family ID | 39560900 |
Filed Date | 2016-03-31 |
United States Patent
Application |
20160093900 |
Kind Code |
A1 |
Brandner; Marco ; et
al. |
March 31, 2016 |
FUEL CELL AND METHOD FOR THE PRODUCTION THEREOF
Abstract
A fuel cell (1) has a plate (2) produced by powder metallurgy
which comprises in one piece a porous substrate area (4) to which
the electrochemically active cell layers (6) are applied, and a
gastight edge area (5) which is provided with gas passages (17,
18).
Inventors: |
Brandner; Marco; (Hofen,
AT) ; Franco; Thomas; (Huttlingen, DE) ;
Kunschert; Georg; (Pflach, AT) ; Zach; Reinhold;
(Reutte, AT) ; Zobl; Gebhard; (Schattwald,
AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Plansee SE |
Reutte |
|
AT |
|
|
Assignee: |
PLANSEE SE
|
Family ID: |
39560900 |
Appl. No.: |
14/956864 |
Filed: |
December 2, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12668963 |
Feb 24, 2010 |
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PCT/EP2008/003630 |
May 6, 2008 |
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14956864 |
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Current U.S.
Class: |
429/535 |
Current CPC
Class: |
Y02P 70/50 20151101;
H01M 8/242 20130101; H01M 2008/1293 20130101; H01M 8/0247 20130101;
H01M 8/0202 20130101; Y02E 60/50 20130101; H01M 8/0232 20130101;
H01M 8/2425 20130101; H01M 8/2483 20160201 |
International
Class: |
H01M 8/02 20060101
H01M008/02; H01M 8/24 20060101 H01M008/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 26, 2007 |
DE |
2007103496 |
Claims
1. A method for producing a fuel cell having a porous substrate (4)
produced by powder metallurgy to which the electrochemically active
cell layers (6) are applied and which is disposed in the central
area of a plate (2) having gas passages (17, 18) provided in the
edge area (5) thereof, the plate (2) being configured in one piece
so as to form a substrate area (4) and the edge area (5), and the
edge area (5) being gas-tightly compressed, wherein a planar,
powder-metallurgical, porous body (24) is produced for forming the
plate (2), the edge area of the body (24) is compressed to the
point of gas-tightness and is provided with the gas passages (17,
18), and the electrochemically active cell layers (6) are applied
to the substrate area (4) of the plate (2), characterized in that
the compression of the edge area of the body (24) to the edge area
(5) of the plate (2) is effected by uniaxial pressing or
rolling.
2. The method according to claim 1, wherein the electrolyte layer
(8) of the electrochemically active cell layers (6) borders
gas-tightly on the gas-tight edge area (5) of the plate (2).
3. The method according to claim 1, wherein the electrolyte layer
(8) of the electrochemically active cell layers (6) extends with
its total circumference at least on a part of the compressed edge
area (5) of the plate (2).
4. The method according to claim 1, wherein the plate (2) is
connected on the circumference gas-tightly to a contact plate
(3).
5. The method according to claim 1, wherein a powder with a
particle size of <150 .mu.m is employed for forming the planar,
powder-metallurgical, porous body (24).
6. The method according to claim 1, characterized in that the
porous body (24) has a porosity of 20 to 60%.
7. The method according to claim 1, characterized in that upon
compression a continuous transition is produced between the
compressed edge area (5) and the intermediate substrate area (4) of
the plate (2).
8. The method according to claim 1, characterized in that the
electrolyte layer (8) of the electrochemically active cell layers
(6) is so applied that it extends at least onto a part of the
compressed edge area (5) of the plate (2).
9. The method according to claim 8, characterized in that the edge
area (5) of the plate (2) is roughened before application of the
electrolyte layer (8).
10. The method according to claim 1, wherein the body is first
sintered to obtain a porous body, and the compression of the edge
area of the body (24) to the edge area (5) of the plate (2) is then
effected by uniaxial pressing or rolling.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of co-pending
U.S. patent application Ser. No. 12/668,963, filed on Jan. 13,
2010, which is a 371 of PCT/EP2008/003630 filed May 6, 2008, which
claim priority to DE 2007103496, filed Jul. 26, 2007, from which
priority is claimed, the disclosure of which is fully incorporated
herein by reference.
BACKGROUND
[0002] This invention relates to a fuel cell having a porous
substrate produced by powder metallurgy to which the
electrochemically active cell layers are applied and which is
disposed in the central area of a plate with gas passages provided
in the edge area thereof. It also relates to a method for producing
the fuel cell.
[0003] Among the various types of fuel cell, the high temperature
fuel cell or solid oxide fuel cell (SOFC) is emerging as
particularly suitable on account of its high electrical efficiency
and the possible utilization of the waste heat arising in the high
temperature range e.g. for stationary cogeneration. It is thus
possible to obtain electrical efficiencies of 60% to 70% in hybrid
systems in which the SOFC is integrated into gas turbine processes.
But also for mobile applications, for example for supplying onboard
electrical systems (APU--auxiliary power unit) in trucks or cars,
SOFC systems are of great interest. They offer the potential of an
efficient and thus fuel-economizing power supply, whereby both
conventional fuels (gasoline, diesel, natural gas) and pure
hydrogen can be employed.
[0004] While the tubular design is particularly suitable for
stationary power plant applications, the planar SOFC offers
advantages for decentralized stationary and mobile application
because of the shorter current conducting paths and thus higher
areal power density.
[0005] The latest generation of SOFCs has a porous metallic body
which performs as a substrate the support function for the
electrode layers and the electrolyte layer (metal-supported cell,
MSC). The MSC is of interest in particular for mobile applications
because it possesses better thermal cyclability, high mechanical
loading capacity and high reoxidation stability at a low cost of
materials and small cell thickness. In addition, the integration of
an MSC into a fuel stack can be realized by commercially available
soldering and welding processes.
[0006] For the substrate it is customary to employ high-alloy
chromium steel. The substrates employed are in particular porous
bodies produced by powder metallurgy (AT 008975 U1), woven or
knitted fabrics (EP 1318560 A2, WO 02/101859 A2), perforated sheet
metal or expanded metal US 2005/142426 A1, GB 2400723 A, GB 2422479
A). In a planar SOFC the substrate can be welded into a sheet metal
frame produced by fusion metallurgy and having the gas passages,
e.g. the fuel gas and waste gas openings for fuel gas supply and
waste gas removal to and from the fuel cell. Thus there is formed a
plate with the gas passages or manifold in the edge area. The
mutual sealing of the anode-side and cathode-side gas space is
effected via the gastight electrolyte which extends from the porous
substrate area beyond the weld seam onto the sheet metal frame (EP
1 278 259 A2).
[0007] The substrate can be perforated sheet metal (WO 02/35628
A1), or a body produced by powder metallurgy (EP 1278259 A2).
[0008] The disadvantage of the perforated plates lies primarily in
their poor coatability with a fine-structured anode, but also in an
irregular gas distribution to the anode. According to US
2005/0175884 A1 it is hence proposed to provide the holes in the
metal plate at an angle. However, this is difficult and
cost-intensive. According to WO 2004/059765 A2 a filling of the
holes of the plate with anode material is proposed to improve the
coatability of the substrate. However, it has been found that all
holes must be filled without error to guarantee the necessary
process reliability. According to WO 2006/138257 A1 there is
proposed a fine-structured transition element, e.g. a nickel mesh,
between the perforated plate and the anode coating, but this
involves additional costs.
[0009] Compared to perforated sheet metal, porous substrates
produced by powder metallurgy offer better coatability and gas
distribution. To connect the porous substrate gastightly to the
sheet metal frame, the edge of the substrate is compressed to be
gastight, according to EP 1 278 259 A2, before it is welded to the
sheet metal frame to form the plate. However, the integration of
the porous substrate with the sheet metal frame causes
microstructurally different, often also different alloys, to be
interconnected. For thermomechanical reasons this state is
undesirable, because high tensions can be induced into the cell
sandwich. Further, the circumferentially formed weld seam between
the sheet metal frame and the substrate leads to warpage of the
plate. Also, the weld seam itself involves the risk of defects,
which would mean a leakage path between anode side and cathode
side. Moreover, the substrate welded into a sheet metal frame leads
to a high cost of materials, because a high proportion of the sheet
metal becomes waste material upon cutting of the frame.
BRIEF DESCRIPTION
[0010] The object of the invention is hence to provide a fuel cell
which guarantees a reliable-process coating with anode, electrolyte
and cathode and at the same time a suitable basis for the stack
integration of the cell at low material usage.
[0011] This is achieved according to the invention by a one-pieced
plate produced by powder metallurgy whose central area is of porous
configuration to form the substrate, and whose edge area having the
gas passages or the "manifold" is compressed to be gastight.
[0012] For producing the plate of the inventive SOFC there is first
produced a planar, powder-metallurgical, porous body which
preferably consists of an iron-chromium alloy. The body can be
produced here according to AT 008 975 U1.
[0013] That is, it can consist of an alloy comprising
[0014] 15 to 35 wt. % Cr;
[0015] 0.01 to 2 wt. % one or more elements of the group Ti, Zr,
Hf. Mn, Y, Sc, rare earth metals;
[0016] 0 to 10 wt. % Mo and/or Al; 0 to 5 wt. % one or more metals
of the group Ni, W, Nb, Ta;
[0017] 0.1 to 1 wt. % 0;
[0018] balance Fe and impurities, whereby at least one metal of the
group Y, Sc, rare earth metals and at least one metal of the group
Cr, Ti, Al, Mn can form a mixed oxide.
[0019] The selection of the powder fraction for the body must be
made in such a way that defects in the surface which naturally
result from deviations from an optimal packing density are kept
small enough to guarantee good coatability. For forming the planar,
powder-metallurgical, porous body there is preferably employed a
powder fraction with a particle size of <150 .mu.m, in
particular <100 .mu.m. The use of finer powder fractions would
improve coatability further, but entail a worsening of the high
temperature oxidation stability on account of a higher internal
surface.
[0020] From powder and a binding agent there is produced a planar
green body with a thickness of preferably 0.3 to 1.5 mm. After the
debindering of the green body the body is sintered, whereby it has
a porosity of preferably 20 to 60%, in particular 40 to 50%, after
sintering. The porosity is the density of the porous body based on
the density of the alloy.
[0021] Subsequently, the edge area of the porous body is compressed
until it is gastight. The dimensions of the compressed edge area
result from the necessary surface area for the gas passages and
sealing surfaces, in particular with the electrolyte layer and the
contact plate, as to be explained more closely hereinafter. The
contact plate is often also designated an interconnector and is
hence to be understood as such.
[0022] The compression of the body in the edge area can be effected
by uniaxial pressing or section rolling. The transition between the
central porous substrate area of the plate and the compressed edge
area can be configured as a step. However, there is preferably
produced upon compression a continuous, stepless transition between
the substrate area and the compressed edge area, because edges and
similar discontinuities can cause tensions in the plate. To obtain
a tension release in the structure of the plate after the
compression process, there can optionally be added an annealing or
similar heat treatment.
[0023] Subsequently, the tight edge area of the plate is provided
with the gas passages by stamping, punching, cutting or the like.
Optionally, the edge area can be provided with the gas passages in
a process step during compression.
[0024] Also, it is possible to provide the edge area of the plate
with further structures, for example by stamping stiffening
structures and/or connecting structures for example with the
electrolyte layer and/or the contact plate.
[0025] Finally, the electrochemically active cell layers are
applied, i.e. normally the anode to the substrate area of the
plate, the electrolyte to the anode and the cathode to the
electrolyte. The anode can be formed for example by a cermet, for
example comprising nickel and yttrium-stabilized zirconium oxide.
The electrolyte layer is gastight and can consist for example of
yttrium-stabilized zirconium oxide or another oxygen-ion-conducting
ceramic. The cathode consists of an electronically, or
electronically and ionically, conductive ceramic, for example
lanthanum strontium cobalt iron oxide.
[0026] Between the electrolyte layer and the cathode there can be
provided a ceramic diffusion barrier layer, for example comprising
cerium gadolinium oxide. Further, there can be provided a diffusion
barrier also between the substrate (FeCr alloy) and the
nickel-containing anode.
[0027] Coating with the electrochemically active cell layers can be
effected by wet-chemical coating, for example screen printing, or
wet powder spraying with subsequent sintering or by thermal
spraying processes, for example high-speed flame spraying or plasma
spraying.
[0028] To seal the cathode-side oxidant space from the opposing
fuel gas space of the plate, the gastight electrolyte layer must
seal at least a part of the compressed edge area of the plate. To
achieve better adhesion of the electrolyte layer on the compressed
edge area, the edge area is preferably roughened before coating,
for example by a sandblasting process.
[0029] As an alternative to the direct coating of the substrate
area of the one-pieced plate produced by powder metallurgy with a
compressed edge area, the edge area can first be connected to one
or more metallic components, for example the contact plate, before
the coating with the electrochemically active cell layers is
effected.
[0030] The inventive fuel cell or SOFC with a one-pieced plate
having a porous central area as a substrate for the
electrochemically active cell layers and a compressed gastight edge
area with the gas passages and optionally further structures offers
considerable advantages and, above all, cost savings. Thus,
omitting the weld seam between the porous substrate body and the
sheet metal frame substantially reduces the production costs. At
the same time, a considerable material saving is attained. Further,
the manufacturing of said one-part plate has the advantage that no
connection of microstructurally, much less chemically, different
materials is carried out. In addition, there is no danger of leaks
due to cracks or pores in the weld seam. Depending on the
construction of the stack, the one-pieced plate additionally offers
the possibility of reducing the overall height per cell, because
the side, facing the electrochemically active cell layers, of the
porous substrate area in the middle of the plate is located at
least at a level with the compressed edge of the plate, while
according to the prior art, for example EP 1 278259 A2, the edge
area of the substrate rests on the sheet metal frame.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Hereinafter an embodiment of the inventive fuel cell will be
explained more closely by way of example with reference to the
drawing. Therein are shown:
[0032] FIG. 1 a perspective exploded representation of two fuel
cells of a fuel cell stack;
[0033] FIG. 2 a section along the line II-II through the right-hand
part of the two fuel cells according to FIG. 1 in an enlarged
representation;
[0034] FIG. 3 an enlarged representation of the area A of FIG. 2;
and,
[0035] FIG. 4 an enlarged partial representation of a front view of
the porous body upon pressing into a plate with a central, porous
substrate area and compressed edge areas.
DETAILED DESCRIPTION
[0036] According to FIGS. 1 to 3, each cell (1) consists of a
powder-metallurgical plate (2) and a contact plate (interconnector)
(3).
[0037] The powder-metallurgical plate (2) is configured in one
piece and has in the central area a porous substrate area (4) and a
compressed gastight edge area (5), the porous substrate area (4)
being indicated by dashed lines in FIG. 1.
[0038] The substrate area (4) is provided with the
electrochemically active cell layers (6) which consist according to
FIG. 3 of an anode layer (7) on the substrate area (4), a gastight
electrolyte layer (8) on the anode layer (7), and a cathode layer
(9) on the electrolyte layer (8).
[0039] The contact plate (3) can be a sheet metal shaped part which
is provided with a wave structure, channel structure or knobbed
structure (11) or similar projections to form contact portions
(11a) which electroconductively contact the powder-metallurgical
plate (2) and thus the anode layer (7) of the one fuel cell (1),
and a contact portion (11k) in electrical contact with the cathode
layer (9) of the neighboring fuel cell (1).
[0040] According to FIGS. 2 and 3, the powder-metallurgical plate
(2) and the contact plate (3) are connected gastightly on the
circumference at (10), for example by welding or soldering.
Further, the gastight electrolyte layer (8) extends on the
circumference at least over a part of the compressed edge area (5)
of the powder-metallurgical plate (2), as to be seen in FIG. 3.
[0041] Thus, the space (13) is separated gastightly from the space
(14) in which the cathode layer (9) is disposed. The space (13) in
which the anode layer (7) is gastightly enclosed constitutes the
combustion space. It is supplied the fuel gas in the direction of
the arrow (15) shown from the back in FIGS. 2 and 3. The fuel gas
can be e.g. hydrogen, methane or another hydrocarbon. In contrast,
the space (14) is supplied the oxidant, for example air or oxygen,
according to the arrow (16) shown from the back.
[0042] On the anode (7) the fuel, e.g. hydrogen, is oxidized and
thus there are extracted therefrom electrons with cation formation
which are supplied via the contact plate (3) to the cathode (9) of
the neighboring cell (1). The oxidant, e.g. oxygen, accepts
electrons in the cathode reaction, so that e.g. oxygen anions are
formed. The anions formed from the oxidant diffuse through the
electrolyte layer (8) and react on the anode side with the cations
formed from the fuel gas so as to form waste gas, for example water
vapor or carbon dioxide.
[0043] According to FIG. 1, the gastight compressed edge area (5)
of the powder-metallurgical plate (2) of each cell is provided on
each side of the substrate area (4) with a plurality of gas
passages (17) or (18). Likewise, the contact plate (interconnector)
(3) has gas passages (19) or (20) on the edge area. The gas
passages (17) or (18) and the gas passages (19) or (20) of all fuel
cells (1) of the stack are flush with each other.
[0044] While the fuel gas is supplied to the fuel gas space (13)
through the gas passages (17) and (19), the waste gas is removed
from the fuel gas space (13) via the gas passages (18) and (20). By
seals (22) and (23) on the gas passages (17) and (18) of two
neighboring fuel cells (1) the gas passages (17) to (20) are sealed
gastightly from the oxidant space (14).
[0045] The fuel cells (1) are series-connected via the contact
plate (3). That is, current is collected from the uppermost fuel
cell and the lowermost fuel cell of the stack.
[0046] According to FIG. 4, for producing the powder-metallurgical
plate (2) a planar, sintered, porous body (24) is compressed on the
edge between a pressing die (25) and a counter die (26) to form the
compressed gastight edge area (5) and the intermediate
uncompressed, porous substrate area (4).
[0047] The pressing die is preferably so configured that upon
compression a continuous, stepless transition arises between the
compressed substrate area (4) and the edge area (5). In the edge
area (5) the gas passages (17, 18) can then be cut or punched on
opposing sides of the substrate area (4), whereupon the
electrochemically active cell layer (6) is applied to the substrate
area (4), namely the electrolyte layer (8) in such a way that it
extends with its total circumference onto the edge area (5), as
shown in FIG. 3.
* * * * *