The development of thin-film solid oxide fuel cells (TFSOFCs) and a method of fabricating them have progressed to the prototype stage. This can result in the reduction of mass, volume, and the cost of materials for a given power level

Chen, Xin

Ignatiev, Alex

Wu, Nai-Juan

NASA Technical Reports Server

18 NASA Tech Briefs, July 2009
The development of thin-film solid
oxide fuel cells (TFSOFCs) and a
method of fabricating them have pro-
gressed to the prototype stage. A TF-
SOFC consists of the following:
• A fuel electrode (anode) of nickel or
other suitable metal, about 10 microm-
eters thick, made porous in a required
pattern as described below;
• A solid electrolyte deposited on the
anode of 0.5- to 2-micrometer thick-
ness;
• An oxidizer electrode (cathode) in the
form of a layer of a mixed ionic-elec-
tronic conductive oxide deposited to a
typical thickness between 1 and 10 mi-
crometers on the solid-electrolyte face
opposite that of the anode; and
• An electrically insulating structure that
encloses the aforementioned compo-
nents and includes manifolds for the
delivery of fuel to the anode, delivery
of air or other oxidizing gas mixture to
the cathode, and removal of combus-
tion products.
The porosity of the anode in a TF-
SOFC is necessary to enable delivery of
the fuel to the anode side of the solid
electrolyte. The cathode is required to
be porous or at least permeable to the
oxidizer to enable delivery of oxygen
to the cathode side of the solid elec-
trolyte. The solid electrolyte layer is re-
quired to be dense and free of defects
so that neither the fuel nor the oxi-
dizer leaks through it. The relatively
small thickness of the electrolyte also
makes it possible to operate the TF-
SOFC at temperature lower than is
necessary for a thicker-electrolyte fuel
cell of older design. In turn, operation
at lower temperature increases the re-
liability and enables a wider choice of
materials for constructing the 
TFSOFC.
In the fabrication of a TFSOFC,
nickel foil to be used as the anode ma-
terial can be rolled or otherwise
processed to produce an ordered crys-
tal structure so that subsequent epitax-
ial deposition of the solid electrolyte
material on the anode will cause the
solid electrolyte to be also crystallo-
graphically ordered and, therefore, to
be dense and relatively free of defects,
as required. The epitaxial deposition
of the solid electrolyte and the deposi-
tion of the electronically and ionically
conductive cathode layer on the elec-
trolyte can be effected by any of sev-
eral established processes for deposi-
tion of thin oxide films. After
deposition of the solid electrolyte, the
required porosity is introduced into
the nickel by photolithographic pat-
terning and etching.
The cathode layer can be deposited ei-
ther before or after patterning of the
anode. Optionally, to enhance the activ-
ity of the porous anode structure, a
mixed-ionic-and-electronic-conductor
film can be deposited on the anode pat-
terning and etching.
Typically, the total thickness of the
anode/solid electrolyte/cathode sand-
wich of a TFSOFC is only about 15–25
micrometers. Operating at a tempera-
ture between 450 and 500 °C, a TF-
SOFC can utilize hydrogen or methane
as a fuel. The power density of a TF-
SOFC can exceed 10 W/cm3 (10
kW/liter), while the power per unit
mass is ≈3 W/g (or ≈3 kW/kg). Relative
to older thicker-electrolyte fuel-cell de-
signs, TFSOFC designs can reduce
costs of materials and reduce the vol-
umes and masses of fuel cells capable
of a generating a given amount of elec-
tric power.
This work was done by Xin Chen, Nai-
Juan Wu, and Alex Ignatiev of the Univer-
sity of Houston for Marshall Space 
Flight Center. 
For further information, contact Sammy
Nabors, MSFC Commercialization Assistance
Lead, at sammy.a.nabors@nasa.gov. Refer to
MFS-32513-1
Thin-Film Solid Oxide Fuel Cells
Mass, volume, and the cost of materials can be reduced for a given power level.
Marshall Space Flight Center, Alabama
aged in light- and radiation-resistant,
easy-to-use dispensers. The resins in the
tapes would be formulated to be curable
by low-power light at specific wave-
lengths that could be generated by
light-emitting diodes (LEDs). Each such
tape dispenser would be marketed as
part of a repair kit that would also in-
clude a companion battery-powered
LED source operating at the required
wavelength.
Each tape consists of a fine-weave
fabric impregnated by a resin. On one
side of the tape there is a cover ply that
prevents the tape from sticking to itself
when it is rolled up as in a dispenser.
Depending on the specific intended
application, the cover ply and resin can
be selected such that the cover ply can
be either released from the tape or
cured in place as an integral part of a
repair patch.
The feasibility of the light-curing
tapes was demonstrated in experiments
in which tapes were made from fiber-
glass fabric impregnated, variously, with
(1) cationic epoxy resins plus a sensitizer
that preferentially absorbs light at a
wavelength of 380 nm, (2) free-radical
curing acrylate resins, or (3) blends of
resins of both types. Methods of incorpo-
rating adducts into the epoxies to tailor
their viscosities were developed. The
tapes were applied to aluminum and car-
bon/epoxy composite substrates that
had been prepared by sanding and wip-
ing with alcohol. The resins were cured
by 380-nm light from LEDs. The blends
of resins of both types were found to be
advantageous in that during exposure to
the light, their acrylate components con-
tributed rapid buildup of strength, while
their epoxy components contributed ad-
hesion and longer-term strength.
Poly(ethylene terephthalate) backing
films were shown to pass the needed
380-nm light and, when prepared with
corona treatment, to adhere well as
parts of cured tapes. Peel tests con-
firmed generally high degrees of adhe-
sion to aluminum substrates. Demon-
strations of repairs were made,
including bonding pipes of various ma-
terials together, patching burst pipes,
and patching punctures. A 1-in. (2.54-
cm) patch over a 1/2-in. (1.27-cm)-di-
ameter hole was pressurized to 120 psi
(≈0.83 MPa) without failure or delami-
nation.
This work was done by Ronald Allred and
Andrea Hoyt Haight of Adherent Technologies,
Inc. for Marshall Space Flight Center. For fur-
ther information, contact Sammy Nabors,
MSFC Commercialization Assistance Lead, at
sammy.a.nabors@nasa.gov. Refer to MFS-
32532-1.
https://ntrs.nasa.gov/search.jsp?R=20090027778 2019-08-30T07:31:22+00:00Z


Thin-Film Solid Oxide Fuel Cells

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server