Segmented cell testing for cathode parameter investigation

P. Tanasini, J. A. Schuler, Z. Wuillemin, M. L. Ben Ameur, C. Comninellis, and J. Van herle

European Fuel Cell Forum Lucerne, July 2nd 2010

ENIFuelCells

Industrial Energy Systems Laboratory (LENI), Group of Electrochemical Engineering (GGEC), Interdisciplinary Centre of Electron Microscopy (CIME)

École Polytechnique Fédérale de Lausanne – EPFLLausanne - Switzerland

OUTLINE

Introduction

Experimental

Results

Conclusion

• Validation• Parameter investigation

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INTRODUCTION (1)- motivation -

Objectives: Reduce testing time Increase reproducibility

0.4

0.5

0.6

0.7

0.8

0 250 500 750 1000 1250 1500 1750 2000

Pot

entia

l [V

]

Time [h]

0.6 A/cm2, 850°C, 7%H2O/H2

And more…… for each experiment!!

Button cell testing:

• Low degradation

Long testing time

• Fluctuations

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INTRODUCTION (2)- strategy -

• N-fold decrease of testing time

• Same T, gas concentration, history

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EXPERIMENTAL- the testing station -

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I

I

RESULTS (1)

1. Validation

2. Parameter investigation• Current density• Cathode thickness• Cathode composition

• Cr source

Anode-Supported (AS) cells

Electrolyte-Supported (ES)

cells

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RESULTS (2)validation

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4 IDENTICAL CELLS

700

800

900

1000

1100

0 200 400 600 800

Pote

ntia

l [m

V]

Current [mA/cm2]

AS-A IAS-A IIAS-A IIIAS-A IV

IV-CURVES

• Similar behavior• Small difference in OCV• Polarization lowers the difference

850°C, 97%H2/3% H2O

0

0.1

0.2

0.3

0.4

0 0.2 0.4 0.6 0.8 1 1.2

-Z'' [

Ohm

cm2 ]

Z' [Ohm cm2]

AS-A IAS-A IIAS-A IIIAS-A IV

~3 hzEIS MEASUREMENTS

• High frequency overlapping• Low frequency mismatch

(conversion process)

H2O/H2 distribution850°C, 97%H2/3% H2O

RESULTS (3)current density

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• Polarization-driven activation

• Current-dependent degradation

0.30 A/cm2

0.45 A/cm2

0.60 A/cm2

0.75 A/cm2

0.30 A/cm2

850°C, 97%H2/3%H2O

• Activation at 0.3 A/cm2

• Operation at different I

RESULTS (4)cathode thickness

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850°C, 93%H2/7% H2O, 0.6A/cm2

20µm

15µm10µm

5µm • Different thicknesses

• Operation 0.6 A/cm2

• Difference in Rohm at the beginning

• AS-B I limited by thickness

• Different degradation behavior:

Thickness Degradation5µ 6.0%/1000h

10µ 2.2%/1000h

15µ 1.5%/1000h

20µ 0.9%/1000h

Cr contamination (SEM, WDX)

RESULTS (5)cathode composition

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• LSM/Mn-doped YSZ cathodes

• Same microstructure (except AS-C II)

600

700

800

900

1000

1100

0 0.2 0.4 0.6 0.8 1

Pote

ntia

l [m

V]

Current [A]

AS-C I (0%Mn-YSZ/LSM)AS-C II (2.5%Mn-YSZ/LSM)AS-C III (4.5%Mn-YSZ/LSM)AS-C IV (6.5%Mn-YSZ/LSM)

850°C, 93% H2/7% H2O

EIS analysis with variation of:

Temperature (750°C, 800°C, 850°C)

Current density (OCV, 0.3 A/cm2, 0.6 A/cm2)

Fuel composition (93%H2/7%H2O, 65%H2/7%H2O, 65%H2/5%H2O)

Frequency Process

10 Hz Conversion, anode

30 Hz (750°C)Dissociative adsorption,

cathode70 Hz (800°C)

200 Hz (850°C)

200 HzDiffusion, anode

(not clear, small signal)

700 Hz (750°C)

Charge transfer, anode1000 Hz (800°C)

2000 Hz (850°C)

RESULTS (6)Cr source

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• WE (cathodes) exposed to Cr source

• One polarized cell, 3-electrode measurements

• One cell at OCV, symmetric cell measurements (4-electrode configuration)

Separation of the cathodic contribution in the polarized cell

The non-polarized cell doesn’t show degradation -0.10

-0.05

0.00

0.05

0.10

0.15

0.70 0.80 0.90 1.00 1.10 1.20 1.30

-Z" [

Ohm

cm2 ]

Z' [Ohm cm2]

120h264h336h432h

800°C, 0.2 A/cm2, air both sides

The multicathode strategy permits to decrease n-fold the testing time

Same testing environment, history for all the segments

Rapid identification of issues by comparison

Flexibility comparable to the classic button-cell testing

CONCLUSIONS12/13

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THANK YOUfor your attention