WP 1: Fuel Cell Development 1 Strictly Confidential NMW Workpackage 1: Fuel Cell Development KTI...
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WP 1: Fuel Cell Development1
http://www.nonmet.mat.ethz.ch/research/onebat
Strictly Confidential
NMW
Workpackage 1: Fuel Cell Development
KTI Review Meeting, December 16, 2005
U. P. Muecke (NMW) and S. Rey-Mermet (EPFL)
NTBINTERSTAATLICHE HOCHSCHULEFÜR TECHNIK BUCHS
WP 1: Fuel Cell Development2
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Project Management
Thermal System
Fuel Cell
Gas Processing
WP 1: Year 1 Milestones
• performance 200 mW/cm2 @ 550°C• external electrical connections
• butane conversion rate > 90%• post-combustor with gas oxidation
> 98%
• battery expert• industrial partner
• thermal insulation concept with Tinside 550°C, Toutside 50°C, <10 cm3
• structures for validation critical points• thermal system demonstrator with simulated 2 W heat source
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Main Achievements after 6 Months
First cell working at 12 mW / cm2
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WP 1: Overview and StructureNMW
NTBINTERSTAATLICHE HOCHSCHULEFÜR TECHNIK BUCHS
ElectrolyteAnode
Cathode
Spray pyrolysisPulsed laser
deposition
Sputtering
CathodeLa0.6Sr0.4Co0.2Fe0.8O3
ElectrolyteCe0.8Gd0.2O1.9,
Y0.08Zr0.92O2-x
AnodeNi-Ce0.8Gd0.2O1.9
Substrate & DesignGlas Ceramic
Substrate & DesignSilicon & Ni grid
AnodeNi-Ce0.8Gd0.2O1.9
ElectrolyteCe0.8Gd0.2O1.9
Cathode
La0.7Sr0.3CoO3
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WP 1 Overview
• WP 1.1 Electrolyte
– fabrication, electrical conductivity
• WP 1.2 Ni/CGO anode thin film
– morphology, electrical conductivity, electrochemical characterization
• WP 1.3 LSCF cathode
– morphology, electrical conductivity, electrochemical characterization
• WP 1.4 Microfabrication and contacting
• WP 1.5 PEN Integration and testing
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WP 1.1 Electrolyte Fabrication
200 nm
200 nm
Substrate in all cases sapphire.
200 nm
Ce0.8Gd0.2O1.9-x
200 nm
Spray pyrolysis (SP)
Pulsed laser deposition (PLD)
• dense and crack-free electrolyte films
• thickness 100-500 nm
sapphire
Ce0.8Gd0.2O1.9-x
(sputtered Pt)
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WP 1.1 Electrolyte Properties
-35 -30 -25 -20 -15 -10 -5 00.1
1
10
100
1000
log
cond
uctiv
ity [S
/m
log pO2 atm
900°C 800°C 700°C 600°C
Electrical conductivityThermal stability
• ionic conductivity ~ 1 S/m at 700° C in air
• predominant ionic conductor for T < 600° C
• high thermal stability for T < 1100° C
no grain coarsening
no long term degradation
Ce0.8Gd0.2O1.9-xCe0.8Gd0.2O1.9-x
-5 0 5 10 15 20 25 30 350
20
40
60
80
100
120
140
160
180
200
220
240
260
2801200° C
1100° C
1000° C
900° C
800° C700° C
Ave
rage
gra
in s
ize
d n
m
Dwell time h
600° C
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WP 1.1 Alternative Electrolyte - YSZ
1 µm
Spray pyrolysis processing
6 8 10 12 141E-3
0.01
0.1
1
10
1001100 1000 900 800 700 600 500
T °C
Con
duct
ivity
S/m
10000 / T K
1.18 eV
Electrical conductivity
• dense and crack-free electrolyte film • ionic conductivity ~ 0.75 S/m at 700° C in air
Y0.08Zr0.92O2-xY0.08Zr0.92O2-x
1.18 eV
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WP 1.2 Electrolyte Conclusions
• Crack-free and dense CGO (SP and PLD) and YSZ (SP) films
• Ionic conductivity surpasses milestone
• Good thermal stability
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WP 1.2 Morphology of Ni/CGO Anode
• crack-free
• > 30% porosity
• 100-1000 nm thickness possible
conventional Ni-YSZ cermet
200 nm
ETH spray pyrolysis (top and cross)
200 nm200 nm
EPFL sputtering (top and cross)
200 nm
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0 20 40 60 80 100 12010-5
10-4
10-3
10-2
10-1
100
101
102
103
104
105
106
time [h]
cond
uctiv
ity [
S/m
]
0
100
200
300
400
500
600
700
800
temp [°C
]
AD_4PT_02
Conductivity of 60/40 Ni-CGO anode
metallic
conductivity
550 S/cm @ 600°C
literature:
400-800 S/cm
degradation:
0.85%/1000 hours
milestone100 S/cm
Yin et al. 2004Pratihar et al. 2005
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2.5 5.0 7.5 10.0
-5.0
-2.5
0
2.5
Z' [ohm cm2]
Z''
[ohm
cm
2 ]
A vs. ARA vs. CR
Electrochemical Characterization - Intro
Rp
I
Total Cell (A vs. C)
Half Cell (A vs. R)Up
U
Ni-CGO anode film
Electrochemical Impedance
Spectroscopy (EIS)
polarization resistance
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0 5 10 15 20 25
-20
-15
-10
-5
0
5
Z' [ohm cm2]
Z''
[ohm
cm
2 ]
60/40 Ni/CGO, T = 650°C
H2O=0%, U=1.210VH2O=0.1%, U=1.168VH2O=0.5%, U=1.124VH2O=1.0%, U=1.100VH2O=3.0%, U=1.057VH2O=3.2%, U=1.052VH2O=4.2%, U=1.043VH2O=6.1%, U=1.027V
Rp as a function of fuel gas H2O content
Water vapor in the fuel decreases Rp in low frequency part
H2O
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0 5 10 15 20 25
-20
-15
-10
-5
0
5
Z' [ohm cm2]
Z''
[ohm
cm
2 ]
60/40 Ni/CGO, T = 650°C
Up=0mV (U=1.215V)Up=20mV (U=1.195V)Up=50mV (U=1.165V)Up=100mV (U=1.115V)Up=200mV (U=1.015V)
Rp as a function of polarization
Anodic overpotential=> production of water
I
Up
Ui
same effect as adding H2O to fuel => Rp decreases
Up
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Rp - comparison water/polarization
PO2
0
2
4
6
8
10
12
14
16
18
1 1.05 1.1 1.15 1.2 1.25U [V]
Rp
[o
hm
cm
^2]
R2 H2OR3 H2OR2 overpotentialR3 overpotential
water in anode gas PH2 / PH2Oapplying overpotential Up
2.5 5.0 7.5 10.0
-5.0
-2.5
0
2.5
Z' [ohm cm2]
Z''
[ohm
cm
2 ]
A vs. ARA vs. CR
R2 R3
equivalent circuit fitting
diffusion accountsfor changes
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WP 1.2 Anode - Conclusions
• 0.1-1 μm thick crack-free films with >30% porosity
• Conductivity surpasses milestone by factor 5
• Conductivity stable over 1500 hours at 550°C
• Good electrochemical performance in dry and humidified gas
Next:
• Improved low temperature sintering
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WP 1.3 Cathode Microstructure & Conductivity
Porosity > 20 % is achieved by spray pyrolysis.
1 μm1 μm1 μm A
500 nm500 nm500 nm C
Good electrical conductivity.
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WP 1.3 Cathode Phase
Desired perovskite phase is obtained.
La0.6Sr0.4Co0.2Fe0.8O3
ETH
La0.3Sr0.7CoO3
EPFL
2 Theta / deg
J. ten Elshof, J. Boeijsma, Powder Diffr, 1996, 11 (3), 240.G.C. Kostogloudis, C. Ftikos, Solid State Ionics, 1999, 126 (1-2), 143.
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Rp
/ cm
2
WP 1.3 Cathode Performance
J.A. Lane, P.H. Middleton, H. Fox, B.C.H. Steele, J.A. Kilner, In 2nd International Symposium on Ionic and Mixed Conducting Ceramics. 1994J.M. Ralph, A.C. Schoeler, M. Krumpelt, J. Mater. Sci., 2001, 36 (5), 1161.
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WP 1.3 Cathode Conclusions
• Crack-free films with >20% porosity achieved
• Good electrical conductivity
• Excellent electrochemical performance
Next:
• Exploring new materials, e.g. Ba0.5Sr0.5Co0.8Fe0.2O3
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WP 1.4 Microfabrication and Contacting
Pt
foturan glass
foturan irradiated
foturan glass
anodeelectrolyte
cathode
contacted -SOFC
free-standing membrane
etching
25 mm
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WP 1.5 PEN Integration and Testing
Air
FuelE I
MFC4MV4 (NC)V4
FICR401
V5MV5 (NC) MFC5
FIC501
V10
V9
inert gasN2, Ar, ...
MFC1MV1 (NC)V1
FICR101
fuelH2, CxHy, ...
V2MV2 (NC) MFC2
FICR201
V3
MV3 (NC) MFC3
FICR301
oxygenO2
V7
V6
V8
FI901
high precision flow meterfor calibration
off-gas anode
TIR904
TIR905
off-gas cathode
TIR906
spare access
spare access
pressurizedair
spare access
oven
TICR910
cell
TIR902
TIR907
pressureregulator
flashbackarrester
anode
cathode
TIR903
TIR908
TIR909
spare access
flashbackarrester
gas mixing box
spare access
CV2
CV3
CV4
CV5
CV1
pressureregulator
pressureregulator
pressureregulator
V11
bubbler
V12
Test rig with computer controlled gas supply and data acquisition
Fuel
Inert
Oxygen
Gas mixing unit
Water Cell
Exhaust
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WP 1.5 Measured Cell Performance
T ~ 550°C
OCV 170 mV
Power density
~12 mW / cm2
YSZ PLDNi-CGO (SP)
LSCF (SP)
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WP 1.5 Projected Cell Performance
Projected cell performance based on results obtained for single layers
today
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Actual design fabrication
Membrane
2.4
cm
Ni grid
Current collector
Contact cathode
Contact anode
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Electrolyte membrane Ce0.8Gd0.2O2 (CGO)
Dense, polycrystalline film Ionic conductivity as in bulk ceramics Better than project specs
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Stress control of CGO-film
Stress controlled by annealing in oxygen Freestanding membranes can be fabricated (2 mm) Thermal stability with 150 nm: up to 300 °C
100 % Ar, 15 mT, RT
Oxygen uptake
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Nickel Grid for membrane reinforcement and current collection
2. Current collectoranode
4. CGO 9. Ni grid
100 m
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Free standing CGO membranes with nickel grid
No annealing
Annealing for low stress
100 m
50 m
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Summary Achievements
500 nm500 nm500 nm
Anode
Cathode
Membrane
> 100 S / cm Rp < 1 cm2
> 550 S / cm Rp < 1 cm2
> 0.5 S / cm
to 500°C Stable up
12 mW / cm2
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Validation of Milestones and Deliverables• WP 1.1: Electrolyte
Month 3: - dense and crack-free electrolyte with composition CGO 80/20 (NMW, EPFL)
- conductivity @ 500°C-800°C in air characterized; > 0.2 S/m @ 700°C in air (NMW, EPFL)
- microstructure characterized (NMW, EPFL)
Month 6: - electrical characterization of free standing membrane (NMW, EPFL)
- stress measurements as input for PEN design optimization (EPFL)
- YSZ electrolytes characterized (NMW)
• WP 1.2: Anode
Month 3: - crack-free Ni-CGO films, > 100 S/cm @ 600C, > 30% porosity in reduced state (NMW, EPFL)
Month 6: - electrochemical characterization of NMW and EPFL films (NMW)
- thermal stability and degradation f(T, t) (NMW, EPFL)
- stress measurements (EPFL)
Deliverables:
Month 6: - selected samples NMW EPFL for stress measurements: dimensions: 4`` or 1 cm x 3
cm, substrate: Si or Foturan
Deliverables:
Month 3: - selected samples from EPFL NMW for electrochemical characterization: dimensions to be
specified by U. Mücke
- substrate: YSZ polished bulk pellet (from NMW)
Month 6: - selected samples from NMW EPFL for stress measurements: dimensions: 4`` or 1 cm x 3 cm,
substrate: Si or Foturan
ongoing
ongoing
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Validation of Milestones and Deliverables• WP 1.3: Cathode
Month 3: - crack-free LSCF films, > 100 S/cm @ 600C, > 20% porosity (NMW, EPFL)
Month 6: - electrochemical characterization of NMW and EPFL films (NMW)
- stress measurements (EPFL)
• WP 1.4 Microfabrication and Electrical Contacting
Month 3: - design of standard PEN and of electrical contacts available (NTB, NMW, EPFL)
- first microstructured PEN elements ready for testing (NTB, NMW, EPFL)
- proof of concept for Ni grid (EPFL)
Month 6: - re-design of PEN element and electrical contacting (NTB, NMW, EPFL)
- Integration of Ni grid in process flow (EPFL)
Deliverables:
Month 3: - selected samples from EPFL NMW for electrochemical characterization: dimensions to be
specified by D. Beckel
- substrate: CGO polished bulk pellet (from NMW)
Month 6: - selected samples from NMW EPFL for stress measurements: dimensions: 4`` or 1 cm x 3 cm,
substrate: Si or Foturan
Deliverables:
Month 3: - first microstructured PEN element NTB, EPFL NMW for testing: dimensions to be
specified by U. Mücke
Month 6-12: - continuous supply of thin films and PEN elements for testing: NTB, NMW, EPFL
ongoing
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Validation of Milestones and Deliverables• WP 1.5: PEN Integration and Testing
Month 3: - test rig for PEN characterization operating (NMW)
Month 6: - first electochemical testing results of integrated PENs (NMW, EPFL, NTB)