Lecture 3 Technologies, scaling up and devices

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Lecture 3 Technologies, scaling up and devices

• Bin Zhu, 1e forskare, docent
• (KTH, www.kth.se)
• Professor at Harbin Engine. Univ.
• Tel.[phone] Fax [phone]
• emailbinzhu_at_ket.kth.se, binzhu_at_kth.se
• Homepage www.ket.kth.se/avdelningar/krt

Biomass and fuel cells lecture at Helsinki
Univ. of Tech., 2005-10-11
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Key concerning points

• Technical solutions from materials to devices
• scaling up is the key to realise the device
• Component fabrication and device construction

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Content
Background and Challenges
From materials devices
Composites, nano-comp. Two phase materials
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Scalling up
Typical cell MEA configuration/fabrication
Cathode active layer (50 -100 um)
Electrolyte 100 500 um
Anode functional layer (ab. 20um)
Anode support
Various fabrication tech./appro.
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Many technical and engineering taskshave been
carried out

• Substrate
• Anode
• Electrode functional layers
• Electrolyte
• Cathode
• Fabrication protocols
• Single cell/test evalustion
• Scale up processes (12x12 cm2)
• Stack/construction and evaluation (1 kW
  progressing)
• iii) Construct FC devices for various fuels
  evalustions/
• applications (H2, H2S, NG, Alcohol,
  Methanol, ethanol, Gasoline, Coal gas,
  Biomass/bio gas

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Substrate

• State of art Ni, Ceria, GCO etc. based
  composites
• Study/develop Ceria, GCO, SCO etc. ITSOFCs
• Ni/ceria composite for strength
• Ni/Ceria-composites (Co, Fe., Cr, Mn etc)
  compatibility electrolte and electrode
• Cu/Ceria-composites (Co, Fe., Cr, Mn etc)
  compatibility electrolte and electrode and
  prevent C deposition
• Optimisation and morphology
• Develop protocles preparations and fabrications

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Electrolyte

• Stater of art
• ceria-based composites CSCs and COCs series
• Establish CSC and COC series
• Developing Manufacturing spects
• Study/develop
• Other combinations, concept manufacturing
  specifications, optimisations
• Concequency and consultancy
• Develop protocles preparations and fabrications
• Develop and suppl all materials (powders)

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Anode

• Stater of art
• Ni (Cu), sulfides/ceria-based electrolyte
  composites
• Study/develop
• -Ni(Cu)/ Co, Fe, Mn, Sn etc.-ceira-composite/elect
  rolyte
• -Optimisation and morphology
• -Manufacturing specifications
• Develop protocles preparations and fabrications
• Develop and suppl all materials (powders)

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Cathode

• Stater of art
• NiO (CuO) or PO/ceria-based electrolyte
  composites
• Study/develop
• -NiO(CuO)/ Co, Fe, Mn, Sn etc.-ceira-composite/ele
  ctrolyte
• -Optimisation and morphology
• -Manufacturing specifications
• Develop protocles preparations and fabrications
• Develop and suppl all materials (powders)

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Fabricating/manufacturing
Integration -components -Optimisation -Manufactu
ring specifications Optimising cell assembly
-Strength -flatness performance -Delivery single
cell tests
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Electrode/electrolyte active layer
Materials selection -inventory coatingmaterials
or interactive layers in site -testing and
Optimisation Method of application
-Inventory -Testing Develop and suppl all
materials
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Ultrafine or nano particles electrochemical
double layer structure
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ITSOFC components Tape-casting technology
Alumina-support
CeO2-based
50 cm
Cathode
Anode
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http//www.fz-juelich.de/iwv/iwv1/index.php?index
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Fig. manufacturing the anode substrate by means
of the Coat-Mix process (CM) with subsequent
thermal pressing
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The Coat-mix process is different not-soluble
powders (called fillers) are coated with phenol
formaldehyde resin (named binder). At the same
time defined powder agglomerates are developed,
which can be easily injected to molded paddings
(green body) during the further processing. At
present the manufacturing of the anode substrates
takes place by mixing NiO, YSZ and ethanol in a
roll container using zirconia balls for milling.
The NiO agglomerates existing in the NiO powder
are destroyed and both powders are fineyl
grinded. Thus one receives a homogeneous mud-like
alcoholic suspension of the raw materials. After
transfer into the coating container, phenol
formaldehyde resin is added to the alcoholic
suspension, which dissolves in the existing
alcohol after short warming, so that a slurry in
binder-lotion accrues. In the following step
acidified water with defined supply rate is added
slowly and continuously to this mixture. The
phenol formaldehyde resin is hardly soluble in
water and precipitates again with the addition of
the insoluble phase. The powder grains, which are
held in suspense by milling, are coated in this
phase with the phenol formaldehyde resin and
stick together easily with one another to larger
agglomerates (Coat mixing). After a subsequent
thermal treatment and a washing process one lets
the precipitation settle and filters off the
liquid on a suction filter. The filter cake is
transferred on dishes and dried in a vacuum
condensation drying furnace at low temperature.
The advantage of this manufacturing method is the
fact that with the mixing process no further
additives must be added. This leads to well
reproducible mixing powders with nearly 100
powder yield. The in this way obtained powder is
well processable after sieving lt80µm and can
simply be filled in pressing forms. Under low
pressure, at temperatures above the melting range
of the binder, it can be easily manufactured to
the desired anode substrates. These are very well
manageable and have the size of 300 x 300 x 2
mm3. Other desired substrate thicknesses are
adjustable without problem with appropriate
pressing forms larger substrates could be
manufactured. The substrates manufactured
according to this method exhibit a homogeneous
structure, have the desired pore size and show a
constant shrinkage behaviour after subsequent
sintering.
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Vacuum slip casting process                    
                                       Fig.
vacuum slip casting equipment for production of
planar SOFCs
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• At the vacuum slip casting process, the process
  flow is accelerated using a vacuum. In principle,
  slip casting processes base upon filling a porous
  casting mould with a solid-containing suspension
  (slip). The solvents of the slip will be drawn
  into the pores of the casting mould, taking along
  the solid. The solid is deposited at the outline
  of the casting mould and adds up in a layer
  (sherd) that can be separated from the casting
  mould after drying. For the production of thin
    anode functional layers and   electrolyte
  layers when producing planar Solid Oxide Fuel
  Cells a modified slip casting process is used.
  Here, suspension is applied on a planar, porous
  anode substrate in an special apparatus (see
  picture) and the solvent is drawn through the
  pores. The solids of the suspension deposit, if
  the substrate is aligned planar, evenly on the
  surface. This process to manufacture thin layers
  shows some advantages
• easy and straightforward handling
• serial production, if automated
• excellent Quality of the produced layers
• reproducibility of the layer thickness, uniform
  thickness and structure throughout the layer
• 2 to 50 µm layers realisable
• little waste (the solvent can be re-used)
• long-term stable suspensions can be produced
  without effort
• The disadvantage of this process is the handling
  of large quantities of solvents and the
  limitation in the thickness of the layer. There
  is also a big influence of the structure of the
  substrate (surface topography, pore size, pore
  distribution, density distribution, and
  absorbency) on the quality of the layer in terms
  of voids and impermeability.

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Fig. wet powder spraying process for planar
(left) and tubular (right) geometries
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Wet powder spraying (WPS) is an easy and low-cost
technology to coat planar or three dimensional
surfaces. A suspension composed of solvent,
powder and additives is sprayed by a nozzle. The
thickness of the coating is adjusted by the
amount of spraying regimes with intermediate
drying steps. Various geometries, e.g planar-type
or tubular-type SOFCs can be coated by a PC
controlled x-y-axis system and a rotational
system for the tubes. The thickness 5 - 100µm.
The major parameters affecting the spray result
spray pressure, spray distance, nozzle type
(with varying aperture), viscosity and solid
fraction of the suspension and the grain size
distribution and grain morphology of the powder.
The intermediate drying steps to obtain thicker
layers are necessary to supress cracking during
drying. The major advantages of WPS compared to
screen printing or plasma spraying are the
low-cost fabrication, the flexibility concerning
size and shape of the samples to be coated, and
the easy integration into an industrial process
chain. For the   Jülich SOFC the double
cathode layer consisting of   cathode
functional layer and   cathode were wet powder
sprayed. Additionally the cathode contact layer
is applied on the metallic interconnects by WPS.
Limitations of the technology are the overspray
and the formation of a suspension mist which
needs to be extracted by suction. The overspray
can be recycled.
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Fig. concept of a screen printing (left)
schematic screen printer (right, above) and
screen printing facility (right, below)
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Various physical approaches for thin films

• Plasma spray
• Laser and sputtering
• Explosion

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AFM images for ceria and ceria-based thin films
surface 3-D morphology a)SDC single phase thin
filmb)SDCcomposite (two-phase) thin
film Surface roughness lt10nm. b) forms even
denser film surface almost without hollow
space/hole.
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To develop high-performance LTSOFCs, metal-ceria
composite electrodes
(b)
(a)
1 um
Ni/Al
(a) Below 15 Wt Ni-Al, ionic conductor, e-phase
non-percolation (b) Percolation threshold 30,
e-continuous, e-conductor more significant mixed
e- and i conductor Above the 30 wt is e-
conductor
 
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To develop high-performance LTSOFCs, metal-ceria
composite electrodes
Other key device components
cerment
Sintered surface
Nano-Cu coated on SDC As high-effective catalyste
anode
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Whisker and Fiber-type MnO2 For high performance
cathode
50 nm
MnO2 whisker TEM photograph
Fiber-type MnO2 HEED photograph
Length 200300nm,diameter 2030 nm
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Typical LTSOFC performances SDC-composite
electrolyte better LT performances
Anode SDC-comp.-Ni-Cu Electrolyte SDC-composite
Cathode Lithiated NiO-CuO
1 Wcm-2 (600?C)
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Hybrid H/O2-excellent LTSOFC performance
1 Wcm-2 (600?C)
How low operation temperature can be reached?
Even at as low as 200ºC!
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FC device and electrochemistry

• Key components
• PEN/MEA?
• Two interfaces(A/E and E/C),more important!To
  realise i/e- gap and electrode reactions, no
  profound theory
• R of FC determined by these two interfaces(phase)
  properties.

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CBC electrolyte advances and excellence?
These values have been well reached In lab.
Cells. In thinner, 50-100 um, the Enhancement by
factor 5-10 is expected
IV/RVsS/L, L0.05 cm/500 um iI/SVs/Ls0.7/0
.0514 s
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Scaling up

• Engineering materials?
• Reproducibility material quality control,
  production process, component fabrication/protocle
  ,
• Long time stability etc.

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Scaling up

• Engineering materials?
• Reproducibility material quality control,
  production process, component fabrication/protocle
  ,
• Long time stability etc.

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A two-cell stack performance 500C

• 1W/cm2 (600C)
• gt0.7 W/cm2 (550C)
• (20 mm)
• 600C near 3 W
• 500C 2 W?

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1 cm2 scalled up 2 cm2, 4x4 and 10x10 cm2 cells

• Performances 2 cm2, 4x4 ,
• Thousands tests and ten more thousands tries
  since last year
• Has made the cell reaching so far
• 8 W (0.5 W/cm2)

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10x10 cm2 For ??1-10kW-???????????/CHP and APU
600C