wp 1: fuel cell development 1 strictly confidential nmw workpackage 1: fuel cell development kti...

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




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




Main Achievements after 6 Months

First cell working at 12 mW / cm2




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




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




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)




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




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




WP 1.2 Electrolyte Conclusions

• Crack-free and dense CGO (SP and PLD) and YSZ (SP) films

• Ionic conductivity surpasses milestone

• Good thermal stability




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




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




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




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




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




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




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




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.




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.




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.




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




WP 1.4 Microfabrication and Contacting

Pt

foturan glass

foturan irradiated

foturan glass

anodeelectrolyte

cathode

contacted -SOFC

free-standing membrane

etching

25 mm




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




WP 1.5 Measured Cell Performance

T ~ 550°C

OCV 170 mV

Power density

~12 mW / cm2

YSZ PLDNi-CGO (SP)

LSCF (SP)




WP 1.5 Projected Cell Performance

Projected cell performance based on results obtained for single layers

today




Actual design fabrication

Membrane

2.4

cm

Ni grid

Current collector

Contact cathode

Contact anode




Electrolyte membrane Ce0.8Gd0.2O2 (CGO)

Dense, polycrystalline film Ionic conductivity as in bulk ceramics Better than project specs




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




Nickel Grid for membrane reinforcement and current collection

2. Current collectoranode

4. CGO 9. Ni grid

100 m




Free standing CGO membranes with nickel grid

No annealing

Annealing for low stress

100 m

50 m




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




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




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




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)




First cell working at 12 mW / cm2

Questions ?

wp 1: fuel cell development 1 strictly confidential nmw workpackage 1: fuel cell development kti...

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fuel decreases rp

c half cell

nm slide

function of fuel gas

upup slide

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