Hector Colon, Prabhu Ganesan, Bala Haran, R. E. White and Branko Popov

Department of Chemical Engineering

University of South Carolina,

Columbia, South Carolina 29208

Performance of Titanium Alloy and Co Plated Titanium Alloy for MCFC Current Collector

Outline

Experimental

Objective

Lifetime Limitations

Results

Conclusions

Materials Characterization

Component Material / Properties Problem/Solution

Anode Material Ni+10wt% CrPore size 3 ~ 6 mPorosity 50~70%Thickness 0.5~1.5 mmSp. Area 0.1~1 m2/g

• Creep/Sintering - Ni-Al Alloy

CathodeMaterial Lithiated NiOPore size 6 ~ 9 mPorosity 80~85% as NiThickness 0.5~0.8 mmSp. Area 0.5 m2/g

• NiO dissolution - Stabilized NiO - LiCoO2 cathode - Modified electrolyte

Matrix Material -LiAlO2

Pore size 0.2 ~ 0.5 mPorosity 50~60%Thickness 0.5 mmSp. Area 0.1~10 m2/g

• Sintering/Thermal Stability - Fiber or large particles• Phase stability - -LiAlO2

CurrentCollector

Material SS316 •Chromium Dissolution - Nickel Cladding (Anode) - Fe-Al alloys

Lifetime Limitations

Lifetime Limitations (SS 316)

0

10

20

30

40

50

60

70

80

90

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400

Time (hours)

Chr

omiu

m M

ole

Frac

tion

(x 1

06 )

0

5

10

15

20

25

30

Nic

kel M

ole

Frac

tion

(x 1

06 )

(b)

Ni

Cr

SS 316(After 350 hr of testing)

Lifetime Limitations (SS 316)

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 treatmentsHeat TreatmentCobalt 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 hrCo 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 AnalysisXRD – Crystal Characterization

AAS - Dissolution Studies

Gold Wire (Reference electrode)

50% LiAlO2 / 50% Electrolyte Plug

O2/CO2 Reference Gas

Alumina Tube

Alumina Tube Wall

Heating Block

SS 304 Rod

Perforated SS 304 Current Collector

Electrolyte andSeparator Matrix

Working Electrode

Cathode Gas Inlet

Gold Wire (Reference electrode)

50% LiAlO2 / 50% Electrolyte Plug

O2/CO2 Reference Gas

Alumina Tube

Alumina Tube Wall

Heating Block

SS 304 Rod

Perforated SS 304 Current Collector

Electrolyte andSeparator Matrix

Working Electrode

Cathode Gas Inlet

O2/CO2 Reference Gas

Alumina Tube

Alumina Tube Wall

Heating Block

SS 304 Rod

Perforated SS 304 Current Collector

Electrolyte andSeparator Matrix

Working Electrode

Cathode Gas Inlet

Results (Mo Dissolution)

Dissolution of Mo from Titanium alloy at 650o C

0

5

10

15

20

25

30

35

40

45

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400

Time (hours)

Mol

ybd

enu

m M

ole

Fra

ctio

n (

x 10

6 )

Bare Ti Alloy

Heat Treated Ti alloy

Cobalt plated Ti Alloy

(a)

Heat Treated Ti Alloy

Bare Ti Alloy

Cobalt Coated Ti Alloy

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 (SEM-Micrographs)

Results (SEM-Micrographs)

Cobalt Coated Titanium Alloy(After 350 hr of testing)

Results (XRD-Pattern after 350 hr testing)

Li2TiO3 – Lithium Titamium Oxide

LiTiO2 – Lithium Titamium Oxide

Titanium Alloys (After 350 hr of testing)

Results (Impedance Behavior with Time)

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70 80Zreal ()

-Zim

g (

)

10hr

60hr

107hr

131hr

248hr

344hr

Bare Titanium Alloy

Results (Impedance Behavior with Time)

0

5

10

15

20

25

30

35

0 20 40 60 80 100 120 140

Zreal ()

-Zim

g (

)

18.5hr43.5hr110.5hr139hr159hr208hr308.5hr

Heat Treated Titanium Alloy

Results (Impedance Behavior with Time)

0

10

20

30

40

50

60

0 20 40 60 80 100 120 140 160Zreal ()

-Zim

g(

)

11hr

35hr

85hr

131hr

162.5hr

347hr

Cobalt coated Titanium Alloy

Results (Impedance Behavior with Time)

0

1

2

3

4

5

6

7

0 2 4 6 8 10 12 14 16Zreal ()

-Zim

g (

)

106081203229344

SS 316

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 collectorCobalt coated titanium alloy gives the highest corrosion

resistance

Financial sponsors - Dept of Energy,

National Energy Technology Laboratory

Acknowledgements