Transcript MCFC Research at USC - Department of Chemical Engineering

Performance of
Co Coated Nickel Cathode Prepared by Tape
Casting for Molten Carbonate Fuel
Cells
Prabhu Ganesan, Hector Colon, Bala Haran, R. E.
White and Branko Popov
Department of Chemical Engineering
University of South Carolina,
Columbia, South Carolina 29208
Outline
Lifetime Limitations
Materials Characterization
New Materials
Approach
Results
Conclusions
Lifetime Limitations
Component
Anode
Cathode
Matrix
Current
Collector
Material / Properties
Material
Pore size
Porosity
Thickness
Sp. Area
Ni+10wt% Cr
3 ~ 6 mm
50~70%
0.5~1.5 mm
0.1~1 m2/g
Material Lithiated NiO
Pore size 6 ~ 9 mm
Porosity 80~85% as Ni
Thickness 0.5~0.8 mm
Sp. Area 0.5 m2/g
Material
Pore size
Porosity
Thickness
Sp. Area
g-LiAlO2
0.2 ~ 0.5 mm
50~60%
0.5 mm
0.1~10 m2/g
Material SS316
Problem/Solution
• Creep/Sintering
- Ni-Al Alloy
• NiO dissolution
- Stabilized NiO
- LiCoO2 cathode
- Modified electrolyte
• Sintering/Thermal Stability
- Fiber or large particles
• Phase stability
- a-LiAlO2
•Chromium Dissolution
- Nickel Cladding (Anode)
- Fe-Al alloys
Materials Characterization
Electrochemical Characterization:
Linear Polarization-RP
EIS
Physical Characterizations:
SEM – Microstructure Analysis
XRD – Crystal Characterization
AAS - Dissolution Studies
New Materials
NiO
Ni from NiO
30
La0.8Sr0.2CoO3 coated Ni tape
Ni from LSC coated Ni
20
Co coated Ni tape
10
LiNi0.8Co0.2O2 Tape
0
0
45
90
135
180
225
0.12
Time (Hours)
Ni dissolution (AAS Data)
Polarization Behavior
La0.8Sr0.2CoO3-NiO
NiO
Over potential  (V)
Ni (mole fraction) X 10 6
40
0.08
0.04
0.00
0.00
0.03
0.06
0.09
0.12
Applied Current (A/cm 2)
0.15
Approach
Auto catalytic reduction of Co
onto Ni metal particles followed
by tape casting
Plasticizer
Binder
Milling
Milling
Activation in
Sodium
Hypophosphite
@ 85 ºC
Cobalt Coating
@ 85 ºC
Dispersant
+ Water
Milling
Filtering +
De-Airing
Casting
Binder : Polyvinyl Alcohol
Plasticizer: Glycerol,
Dispersant: Disperbyk®
Results
TGA Behavior of Co coated Ni
green tape
Sintering was performed in
several steps
RT
104
Nickel
r = 10 oC/min
96
-10
-20
92
-30
-40
88
-50
84
-60
80
0
200
400
600
o
Temperature ( C)
-70
800
dw/dT*1000 (mg/o C)
0
100
wt remaining (%)
1 ºC/min.
10
130 ºC for 1 hr
1 ºC/min.
Nitrogen
230 ºC for 3 hr
1 ºC/min.
400 ºC for 5 hr
5 ºC/min.
Hydrogen
800 ºC for 1 hr
RT
Results (SEM-Micrographs)
Co coated Ni
powder green
tape
Sintered Co
coated Ni
powder
Co coated Ni
powder electrode
after immersion
in MC for 200 hr
Co coated
Ni powder
electrode
half-cell
testing after
1000 hr
15 mm
Magnification X 2000
Results (XRD-Patterns)
Ni
9000
5000
Intensity (a.u)
7000
5000
3000
4000
3000
2000
1000
1000
0
0
10
20
30
40
50
60
70
80
90 100
0
10
20
30
2 Theta (deg.)
Ni
NiO
5000
Co-Ni Powder
40
50
60
70
80
90 100
2 Theta (deg.)
6000
Intensity (a.u)
Intensity (a.u)
NiO
6000
4000
After half-cell
Testing (1000 hr)
3000
2000
After immersion
for 200 hr
1000
0
0
10
20
30
40
50
60
2 Theta (deg.)
70
80
90 100
Results (Ni Dissolution)
Dissolution Behavior of Co Coated Ni
Electrode at 650o C
35
Ni mole fraction (x10-6)
30
Co coating on
Ni
powder
(~4 wt. %Co)
followed by
tape casting
and sintering
Ni from NiO
NiO
25
20
Co coated Ni tape
15
10
from CoNi
coated
Ni
CoNicoated
powder
5
0
0
50
100
150
Time (hours)
200
250
300
Results (Impedance Behavior at 650 ºC)
1.5
-Imaginary Z"(
2.0
1.5
-Imaginary Z" ()
0:60:16
1:60:16
2.5:60:16
10:60:16
30:60:16
45:60:16
60:60:16
1.0
Increasing
Increasing COCO
2 2
1.0
33:60:0
33:60:1
33:60:2.5
33:60:5
33:60:10
33:60:20
33:60:30
Increasing
Increasing OO
2 2
0.5
0.5
0.0
0.7
1.2
1.7
2.2
Real Z'()
Varying CO2 Partial Pressure
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Real Z' ()
Varying O2 Partial Pressure
Results (Impedance Behavior at 700 ºC)
0:60:16
5:60:16
33:60:16
60:60:16
-Imaginary Z" ()
-Imaginary Z" ()
2.0
33:60:0
33:60:5
33:60:16
33:60:30
2.0
1.5
1.5
Increasing O2
1.0
1.0
Increasing
CO
Increasing CO
2 2
0.5
0.5
0.0
0.0
0.6
1.2
Real Z' ()
1.8
2.4
Varying CO2 Partial Pressure
0.6
1.2
1.8
2.4
Real Z' ()
Varying O2 Partial Pressure
Results (Impedance Behavior with time at 650 ºC)
-Imaginary Z" ()
2.0
10 h
20 h
40 h
50 h
60 h
82 h
104 h
1.5
82 h
1.0
60 h
50 h
0.5
40 h
0.0
0
1
2
Real Z' ()
3
20 h
10 h
Conclusions
 Dissolution rate of cobalt coated nickel particles is 33%
lower than NiO cathode dissolution
 Dissolution is lower than cobalt coated Ni tape
 Polarization behavior shows similar performance as state
of art NiO
 Impedance shows after 80 hr of operation the system
reaches steady state
Acknowledgements
Financial sponsors - Dept of Energy,
National Energy Technology Laboratory