Transcript MCFC Research at USC - University of South Carolina

Performance of Titanium Alloy and Co Plated
Titanium Alloy for MCFC Current Collector
Hector Colon, Prabhu Ganesan, Bala Haran, R. E.
White and Branko Popov
Department of Chemical Engineering
University of South Carolina,
Columbia, South Carolina 29208
Outline
Lifetime Limitations
Objective
Experimental
Materials Characterization
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
Lifetime Limitations (SS 316)
90
30
Cr
80
(b)
25
60
Ni
20
50
15
40
30
10
20
5
10
0
0
0
25
50
75
100 125 150 175 200 225 250 275 300 325 350 375 400
Time (hours)
Nickel Mole Fraction (x 10 6)
Chromium Mole Fraction (x 10 6)
70
Lifetime Limitations (SS 316)
SS 316
(After 350 hr of testing)
Objective
To find a candidate that will has better corrosion
resistance than the state of art current collector
To characterize the performance of a titanium alloy
(Ti77.5/Mo12/Zr 4.5/Sn 4.5) with different surface
treatments
Heat Treatment
Cobalt platting on the surface
Experimental
Heat treatment was performed in order to increase the
thickness and form a more uniform protective
corrosion layer
 Kept at 400 ºC in 99 % N2 & 1% O2 atmosphere for
62 hr
Co plating was performed to reduce the possible
dissolution of components and to improve the
conductivity of the oxide layer
 Cobalt chloride and sodium citrate bath
 1 mA/cm2 for 2.5 hours at pH 9.5
Materials Characterization
Electrochemical Characterization:
Linear Polarization-RP
EIS
Physical Characterizations:
SEM – Microstructure Analysis
XRD – Crystal Characterization
AAS - Dissolution Studies
Results (Mo Dissolution)
Dissolution of Mo from Titanium alloy
at 650o C
45
Bare Ti Alloy
(a)
Molybdenum Mole Fraction (x 10 6)
40
35
Heat Treated Ti Alloy
30
25
20
Cobalt Coated Ti Alloy
15
Bare Ti Alloy
10
Heat Treated Ti alloy
Cobalt plated Ti Alloy
5
0
0
25
50
75
100
125
150
175 200 225
Time (hours)
250
275
300
325
350
375
400
Results (SEM-Micrographs)
Cobalt coated Titanium Alloy
(Before testing)
Results (SEM-Micrographs)
Bare Titanium Alloy
(After 350 hr of testing)
Results (SEM-Micrographs)
Heat Treated Titanium Alloy
(After 350 hr of testing)
Results (SEMMicrographs)
Cobalt Coated Titanium Alloy
(After 350 hr of testing)
Results (XRD-Pattern after 350 hr testing)
Titanium Alloys (After 350 hr of testing)
Li2TiO3 – Lithium Titamium Oxide
LiTiO2 – Lithium Titamium Oxide
Results (Impedance Behavior with Time)
35
10hr
60hr
107hr
131hr
248hr
344hr
30
-Zimg ()
25
Bare Titanium
Alloy
20
15
10
5
0
0
10
20
30
40
Zreal ()
50
60
70
80
Results (Impedance Behavior with Time)
35
18.5hr
43.5hr
110.5hr
139hr
159hr
208hr
308.5hr
30
-Zimg ()
25
20
15
Heat Treated
Titanium Alloy
10
5
0
0
20
40
60
80
Zreal ()
100
120
140
Results (Impedance Behavior with Time)
60
11hr
35hr
50
85hr
131hr
162.5hr
-Zimg()
40
347hr
30
20
Cobalt coated
Titanium Alloy
10
0
0
20
40
60
80
Zreal ()
100
120
140
160
Results (Impedance Behavior with Time)
7
10
60
81
203
229
344
6
-Zimg ()
5
4
3
2
1
SS 316
0
0
2
4
6
8
Zreal ()
10
12
14
16
Conclusions
 Immersion test indicate a decrease in molybdenum
dissolution in the case of Cobalt coated Ti alloy
 Surface mainly consist of Titanium oxides
 The polarization resistance for this alloy is significantly
higher than state of art current collector
 Cobalt coated titanium alloy gives the highest corrosion
resistance
Acknowledgements
Financial sponsors - Dept of Energy,
National Energy Technology Laboratory