SOFC Development at GE Global Research

Matt AlingerGE Global ResearchNiskayuna, NY SOFCSOFC

12th Annual SECA WorkshopPittsburgh, PAJuly 26-28, 2011

2SECA Annual Workshop

July 2011

Aligned for growth

GE Capital

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GE today

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July 2011

Global reach and connectivity

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40,000 technologists across GE

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Diagnostics & Biomedical Technologies

Appliances WaterLightingEnergy TransportationAviation Healthcare

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4SECA Annual Workshop

July 2011

Global Research annual funding

• Advanced Technology programs

• New ideas

• High-risk/high reward

• Next generation product technology

• Short-term technical challenges

• Joint technology

• Specific customer focus

~$600 M

52%55%

28%

17%

GE business programs

GE corporate programs

External partnerships and gov’t. funded

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July 2011

Technology Challenges for SOFCs

• Materials set High power densityLow degradation / stable

• Scale-upLarger cellsBigger stacks

• System design & integration Improved design for reliabilityOperability (start-up, shut down, transients, …)

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Presentation Outline

• Materials Set– Cost– Performance– Degradation

• Scale-up– Manufacturing

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Materials Set

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Anode Supported Solid Oxide Fuel CellLayer Function Material Thickness

Air Side

Interconnect Gas & Electron Transport Ferritic Stainless Steel 500 m

Protective Coating Prevent interconnect Cr from poisoning cathode (Mn,Co)3O4 10 m

Cathode Contact Paste

Electrically connect cell with air interconnect (La,Sr)CoO3 100 m

Cathode Air electrode (La,Sr)(Co,Fe)O3 40 m

Barrier Layer Prevent cathode Sr from reacting with electrolyte Zr

GDC(Ce0.8Gd0.2)O2

10 m

Electrolyte Permit O2- transport, prevent air/fuel mixing

YSZ(ZrO2 + 8 mol Y2O3)

10 m

Fuel Side

Functional Anode Fuel electrode NiO/YSZ 20 m

Anode Support Mechanically supports Anode & Electrolyte NiO/YSZ 200 m

Anode Contact Paste

Electrically connect cell with fuel interconnect NiO 100 m

Interconnect Gas & Electron Transport Ferritic Stainless Steel 500 m

9SECA Annual Workshop

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21 atm, 800oC, 64%H2-36%N2, 80% Fuel Utilization (Uf), 0.7V

Significant performance improvementSufficient to meet cost targets, though higher

performance directly impacts stack cost

Performance status

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0

0.25

0.5

0.75

1

Baseline Cost Increased PowerDensity

Low-costinterconnect

Nor

mal

ized

sta

ck c

ost

0.5

W/c

m2 ,

E-Br

ite

0.75

W/c

m2 ,

E-Br

ite

0.75

W/c

m2 ,

441S

S

Stack cost status

Cost reduction through performance improvement and interconnect alloy

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Degradation reduction

-Developed interconnect coating-Stabilized cathode-Validated low-cost interconnect alloy

Degradation mechanisms identified and mitigation

strategies validated

Cost and degradation risk significantly reduced

Engineering solutions exist, however, significant work remains to understand degradation

fundamentals.

800oC, 1.25A/cm2, 441SS

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Location-specific degradation can be measured from embedded gold mesh

(voltage point)

Measurement of location-specific degradation

Steel Interconnect V1

V2

Gold Interconnect

Anode votlage lead

Gold current collectorSteel current collector

V1

V2

Anode

ElectrolyteCathode

Contact paste

Gold mesh

Test Conditions: 800oC1.25 A/cm2

H2+3%H2O

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ASR degradation from power curves

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0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0 3 5 0 0

F S S 1

F S S 2

F S S 3

A u 1

A u 2

A u 3

ASR

, m

-cm

2

t im e , h

18 m - c m 2 /1 0 0 0 h

63 m - c m 2/ 10 0 0h

7 4 m - c m 2 /1 00 0 h2 5 m - c m 2/ 10 0 0h

8 m - c m 2 /1 00 0 h

15 m - cm 2 /1 0 0 0 h

ASR degradation consistent with traditional cell construction

Test conditions800oC

1.25 A/cm2

H2+3%H2O

ASR from weekly power curves @ 0.7V

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Non-ohmic degradation

Generally indicative of loss of electrochemical

contact

No catalytic activity loss

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-20

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FSS 1

FSS 2

FSS 3

Au 1

Au 2

Au 3

A

SRno

n-oh

mic, m

-c

m2

time, h

-2 m-cm2/1000h

35 m-cm2/1000h

39 m-cm2/1000h

3 m-cm2/1000h

-1 m-cm2/1000h

0 m-cm2/1000h

Non-ohmic degradation is nearly zero

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Ohmic Degradation

Measured degradation is nearly all ohmic in nature

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F S S 1F S S 2F S S 3

A u 1A u 2A u 3

A

SRoh

mic, m

-c

m2

t im e , h

2 0 m - cm 2 /1 00 0 h

28 m -c m 2/ 10 0 0 h

3 5 m - cm 2 /1 00 0 h

2 2 m -c m 2/ 10 0 0h

9m - cm 2 /1 0 0 0 h

1 5 m - cm 2 /1 00 0 h

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Interfacial ASR

Confirms contact resistance data

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A

SRco

ntac

t res

ista

nce, m

-c

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time, h

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FSS 1

FSS 2

FSS 3

Au 1

Au 2

Au 3

A

SRin

terfa

cial

, m

-cm

2

time, h

3 m-cm2/1000h

3 m-cm2/1000h

8 m-cm2/1000h

0 m-cm2/1000h

0 m-cm2/1000h 0 m-cm2/1000h

ASR(contact resistance testing)

V

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Manufacturing

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Metal supported cell

Advantages:Integrated anode sealElectrolyte in compressionImproved anode electrical

contactIncreased active areaLower anode polarizationAllows redesign of structures

Challenges:Dense / hermetic electrolytePorous metal substrate degradation

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Low-cost manufacturing

Thermal Spray

Extrusion Lamination

Electrolyte

Electrode Layers

Thin Electrolyte Bilayer

Cutting Sintering Electrode Application

FiringSintered Cell Manufacturing

Leverage GE thermal spray expertise

Sheet Metal Fab Joining

Complete Interconnect

PreSealing StackingAdvantages

Larger area / ScalableSimplified sealingLow Capex / ModularLean Manufacturing

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Cell Manufacturing Processes

Enable larger, thinner cellsExploration of different processes and cell structuresGoal is to demonstrate scalability

Disruptive to stack manufacturing cost structure

Atmospheric Plasma Sprayporous cathode

dense electrolyte

porous anode

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High throughput, many different structures / compositions / formats can be tested

Cell and stack design tailored to deposition processes

Performance reaching sintered cell levels

Scale-up to 4’’ and 12’’ cell on-going

Deposition Technology Progress

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Discontinuous coating Continuous coating

Smooth Anode Development

Minimum thickness required for deposition of a continuous anode on a porous substrate.

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Anode thickness

Ano

de ro

ughn

ess

on Ni foam Aon Ni foam BSupport ASupport B

0.001

0.01

0.1

1

10

100

1000

Anode thickness

Leak

rate

(sc

cm/c

m2)

on Ni foam Aon Ni foam Bblank

Support ASupport B

foam roughness

Anode roughness initially decreases with increasing thickness, then stabilizes to a fairly constant value. Transition is indicative of full foam coverage.

Leak rate decreases with increasing anode thickness until it stabilizes, which is indicative of full foam coverage.

foam leak rate

Minimum thickness established for full foam coverage with smooth anode

Smooth Anode Development

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Smooth Anode Development

Deposition condition developed for smooth anode deposition onto foam support

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1” diameter foam coated with smooth anode. Surface is generally smooth, however a few localized defects can be identified.

Manufacturing defects may impact cell performanceImproved process control for removal

Smooth Anode Development

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Effect of surface asperities on stress-state of thermal sprayed coating

• Asperities cause local stress gradients in electrolyte

• Effect enhanced after anode reduction

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2 mm

5 mm

Top-down view of deposited coating on 1” diameter button cell

Electrolyte optimization

With a smooth anode & control of defects, high quality electrolytes can be deposited.

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Thermal spray heat flux modeling

Thermal heat flux modeling to support large area cell

thermal management

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In-situ measurements in the spray cell permit rapid feedback for development

OCV measurement

OCV mapping can be performed across entire cell

Thermal Imaging

In-situ characterization for thermal sprayed cells

Touch probe

OCV reading Gas feed

Back-heating

Imaging during OCV testing helps in further cell characterization

IR camera image

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Thermal Sprayed Cells (25 cm2)

Optimizing electrodes and electrolyte for improved power density

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Current Density (A/cm²)

Improved structures

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Summary• Identified high-impact fundamental degradation mechanisms and

developed cost-effective mitigation solutions.

• Demonstrated high, stable performance of LSCF-based cathode SOFCs with gold current collectors.

• Demonstrated parabolic power density degradation behavior with ferritic stainless steel (AL441HP) current collectors that is indicative of chromia scale growth.

• Implemented and tested an integrated thermal spray manufacturingsystem for SOFCs.

• Identified anode roughness as a key criteria to enable hermeticelectrolytes.

• Developed thermal spray conditions to produce a smooth fuel electrode (anode) on a porous metal support.

• Demonstrated operational performance on 25cm2 thermal sprayed cells.

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Acknowledgements

• Joe Stoffa, Briggs White, Travis Shultz, Heather Quedenfeld and Shailesh Vora of DOE/NETL

• Funding provided by the US Department of Energy through cooperative agreement DE-NT0004109.

• SECA partners• GE SOFC Team

This material is based upon work supported by the Department of Energy underAward Number DE-NT0004109. However, any opinions, findings, conclusions, orrecommendations expressed herein are those of the authors and do not necessarilyreflect the views of the DOE.