Development of a Thermal Spray, Redox Stable, Ceramic ... Library/Events/2017/sofc...

Imagination at work.

Richard Hart GE Global Research Pitt Review June 12, 2017

Development of a Thermal Spray, Redox Stable, Ceramic Anode for Metal Supported SOFC

SOFC Innovative Concepts and Core Technology Research DE-FOA-0001229 Award FE0026169

*

*Trademark of General Electric Company

GE Confidential - Distribution authorized to individuals with need to know only. © 2015 General Electric Company - All rights reserved

2

Metal supported SOFC cells

Advantages:

Integrated anode seal

Electrolyte in compression

Improved anode electrical

contact

Increased active area

Lower anode polarization Challenges:

Dense / hermetic electrolyte

Porous metal substrate degradation

Porous Metal Substrate


3

Low-cost manufacturing

Thermal Spray

Extrusion Lamination

Electrolyte

Electrode Layers

Thin Electrolyte Bilayer

Cutting Sintering Electrode Application

Firing Sintered Cell Manufacturing

Leverage GE thermal

spray expertise

Sheet Metal Fab Joining

Complete

Interconnect

PreSealing Stacking Advantages

Larger area / Scalable

Simplified sealing Low Capex / Modular Lean Manufacturing


4

Traditional NiO(Ni)/YSZ anodes

• Advantages:

– High initial electrochemical activity

– Good electronic conductivity

– Low cost

– Well understood, wealth of data

• Disadvantages:

– High redox Vol change (fuelair)

– Ni particle ripening/poisoning

– EHS concerns (NiO)

– Sourcing concerns (REACH in Eu)

© 2015 General Electric Company - All rights reserved

5

2017 Project Goals:

Transition WVU Set 2 Materials to GE Thermal Spray

Metal Supported SOFC Cell (100cm2) with:

• >200 mW/cm2 on Reformate Fuel (>50%Uf, 0.7V)

• <10% Degradation after 1000h (or >180mW/cm2)

• >3 Redox Cycles

• ~Equivalent Materials Cost and Process vs. Baseline

5


Cell Testing & Thermal Spray Film

Results


7

Y1 Review – Metal Supported Ceramic Anode Cells

Sourced Engineered Powders LST (La0.35Sr0.65TiO3)

GDC (Gd0.2Ce0.8O~1.9)

100cm2 Cells (2-6 cell stacks) OCV, W/cm2 Redox Stability

Coupon Screening Experiments (Thermal Spray) XRD, SEM, Permeability, DE, Roughness, etc…


8

Redox Cycling – (2 cell stacks)

0

20

40

60

80

100

0 1 2 3 4 5

% o

f In

itia

l O

CV

Cycle

0

20

40

60

80

100

0 2 4 6

% IN

ITIA

L O

CV

CYCLE

Failure! Stable!

Thermal cycles

Redox cycle

Thermal cycle

Redox cycles

Ni/YSZ cells fail after a single redox cycle

Ceramic anode cells survive > 5 cycles

LST/GDC cells = Low power (55-130mW/cm2) –H2/N2 fuel Inherently low material conductivities (e-)


9

Optimization Experiments: LST-GDC co-spray

5_CondA34_condA23_CondA2_CondB1_CondH

130

120

110

100

90

80

70

60

50

40Po

wer

Den

sity

(m

W/c

m2

- 0

.7V

/34

%U

f)

Boxplot - Cell Power Density at 0.7V/34% Uf

- Co-Spray Experiments investigated: Plasma power Feedstock powder calcination Powder injection parameters

- Results limited to < 130 mW/cm2

*Rxn to form new phase *Low film conductivity (LST)

Film conductivity Porosity Good Cohesion TPB -m2/g Stiffness/Cracking Low Cohesion Rxn Phase formation

“Hotter” “Cooler”

Need alternate formulation/method to achieve >200 mW/cm2


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Red = Hot, GRC

Orange = Hot, Vendor B

Dark Green = Cool, GRC

Light Green= Cool, Vendor B

Blue = coldest cond,VendorB

LST-GDC Electrodes: Microstructure, film XRD

GRC Spray Dry

DOE_1199

DOE_1202

DOE_1190

DOE_1193

DOE_1196

Red = Hot, GRC

Orange = Hot, Vendor B

Dark Green = Cool, GRC

Light Green= Cool, Vendor B

Blue = coldest cond, VendorB

-Process opt minimized LST+GDC Reaction *3Q-4Q: alternate methods of GDC/YSZ integration: infiltration/co-feed

Variation in feedstock agglomerate size variation in microstructure/phase/cond -Confirmed this is a key factor to control -2nd Learning: use larger scale up batches (less re-optimization needed)

GRC Pilot Batch

Vendor Batch


11

CasaXP S (Thi s st ring can be edit ed in CasaXPS.DEF/P rintFootNote.txt)

x 10-1

0

2

4

6

8

10

CP

S

468 464 460 456 452Binding Energy (eV)

Sintered pellet, H2 Thermal Spray film

Tested TS film

Ti2p Ti2p3/2

Ti2p1/2

Ti4+-O

Ti3+-O

• Chemically deactivation of doped SrTiO3!

• 2017 Q1-Q2 – noted process changes can be made to reduce/eliminate this effect

*Improved thermal spray film S/cm ~40-100x

XPS High Resolution Spectra *after 1um etching– Chemical Bonding*

Deactivation of doped SrTiO3 (no GDC) in Thermal Spray


12

LST-GDC Mixtures Alt Doped SrTiO3 2ndAlt Doped

SrTiO3 &

Optimized TS

Thermal Spray Anode Film Conductivity Screening

S/cm Target Derived from Echem Model

Achieved sufficient film S/cm (anode chemistry & thermal spray conditions) Next step: focus/balance electrode microstructure +catalyst prop


GE Ceramic Anode Material Screening

Test Results


14

Material Development Testing Plan

Synthesis

• XRD - impurities

• Particle Size

Conductivity Testing

• Screen w/ pressed pellets or free-standing films

• Electron Conductivity > 10S/cm (bulk), >5 S/cm (film)

• Ion Conductivity > 0.5x10-2 S/cm (film)

Mechanical Stability During Redox Cycling (800C)

• Redox Vol. Change < 0.15% V – redox dilatometry

SOFC Cell Testing

• GRC – thermal spray 100cm2 metal supported cells (2-6 cell stacks)


15

Conductivity Test Setup (GE-GRC)

Jezek, Hart


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LST Conductivity – Effect of Sintering Atm, and Redox:

Jezek, Hart

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

0 1 2 3 4

Co

nd

uct

ivit

y (S

/cm

)

Test Time (h)

LST Pellet Conductivity – Redox Cycling

H2 AIR N2 H2

E-chem Model -> need to identify materials w/ >10-20S/cm after redox

-3

-2

-1

0

1

2

3

400 500 600 700 800 900 1000

log

σ (

S/cm

)

Temperature ©

LST – 1450C sintered, effect of atm:

Solatron 1287/1260, 4pt, AC impedance, ~1kHz

LST 1450C, H2 sintering

LST 1450C, Air sintering

LST 1450C, H2 sintering

Conductivity during Redox Solatron 1287/1260, 1kHz, 4pt


17

Summary of doped Strontium Titanate Screening - GE

Factor: Conditions/Ranges: A dopant RE (La, Y, Yb, Lu, Gd, etc…) [0.01>x>0.4]

A-site Def 0-10% B dopant Fe, Nb, Ga, etc.. [0.02>y>0.1]

Firing Temp 1200C-1500C Firing Steps 1-4 Milling Water/EtOH, time Firing Batch Qty/vessel (g), Crucibles vs. Tray

Gas Air, different Reducing Gases

Precursors oxides, carbonates, other salts

Over 100 tested batches @ GE!

(~10g size)

XRD and Redox S/cm

Identified several Promising leads!


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Alternately Doped SrTiO3 – leading candidate

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Redox Conductivity: -Excellent conductivity -Good redox stability

Redox Dilatometry:

-Excellent mechanical redox properties -Material was selected for scale up to larger batch sizes


19

Scale up of Alternately Doped SrTiO3

Batch Size

Redox Cycle

1kg10g

1010

65

60

55

50

45

Sam

ple

Co

nd

ucti

vit

y (

S/cm

)

Boxplot of Sample Conductivity: Effect of Redox cycling and Batch Size

Sample ID Batch Pressing Cond Sintering Conds Initial Cond (S/cm) PostRedox1 (S/cm) Notes

DOE_1351 FC-0202-S1 Std Std 41.2 38.7 Strange Redox Behavior, improved cond in air????

DOE_1354 FC-0202-S1 Std Std 45.2 41.8 Normal Redox Behavior, tiny pellet fracture at end of Test?

DOE_1357 FC-0202-S2 Std Std 52.1 45.5 Strange Redox Behavior, jumpy and improved during air???

DOE_1355 FC-0202-S3 Std Std 1.7 0.97 Strange redox behavior, improved cond in air!!! ~6S/cm!!!

DOE_1353 FC-0202-S4 Std Std 18.1 12 Strange Redox Behavior, improved cond in air????

DOE_1356 FC-0202-S4 Std Std 45.9 43.1

DOE_1358 FC-0202-S5 Std Std 55.3 51.4 Excellent behavior during redox.

May: Produced 17kg batch, Thermal Spray in July

1st compound scaled from 10g 1000g17000g!

Factors: tray type, gas environment/flow, mixing & milling methods, precursors , etc..

Goal: Scale up ~2-3 more down-selected candidates by Fall 2017

GE currently has 2 formulations in the beginning stages of Scale Up

Scale Up 1: 10g->1kg std gas env Scale Up 2: Altered reducing gas environment


WVU & GE Layered Perovskite

Development


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Formulation Development Summary:

GE Global Research:

-Pivot: added on ceramic synthesis efforts:

* Studied doped SrTiO3

* Scale up of WVU formulations -> Vendor Transition

WVU:

-Higher Risk formulations:

* Scheelites – showed low S/cm or mech instability

* Layered perovskites – SrMoO3

-Current focus of WVU research.

-GE currently trying to scale 2 formulations

*West Virginia University *


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Summary of Layered Perovskite Development:

Comp Cond (S/cm)

Mech Redox (dV)

CTE (ppm/C)

Notes

SrMgMo 50 + 14.78 S/cm reduces with redox cycling

SrFeMo 20-148 -- NA Poor redox stability

SrFeCoMo 7.4 - 20.39 Higher S/cm in air

SrMgMo (2) ~30 ++ 15.6 Improved Redox Stability vs baseline SMM

Doped - SrFeMo 15-22 +++ 15.01 Mech and S/cm redox stability


23

F-2 O-2 F-3 O-3

0

5

10

15

20

25

30

35

40

Co

nd

uctivity (

S/c

m)

Atmosphere

SMM Formulation Variation Study:

-Identified higher performing SMM formulations (only 1 variant shown) -continuing optimization work & scale up

Redox S/cm

Redox Dil

Comp B


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0 250 500 750 1000 1250 1500 1750

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

AirAir Forming gasForming gas

Time (minutes)

dL

/L

Air

0

100

200

300

400

500

600

700

800

900

Te

mp

era

ture

(oC

)

0 250 500 750 1000 1250 1500 1750

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

0.018

Time (minutes)

dL

/L

0

100

200

300

400

500

600

700

800Forming

gas

Forming

gas

AirAir

Te

mp

era

ture

in

oC

Air

Redox Dilatometry and Conductivity of SFM vs doped-SFM

Sr2Fe1.5Mo0.5O6-δ Doped SFM, solid state synthesis

CTE in Air, 25-800oC = 17.12x10-6 K-1

CTE in Air, 25-800oC = 15.31x10-6 K-1

Doping Improved redox S/cm stability, Mechanical stability,

And lowered CTE

Initial scale up studies underway

Redox S/cm

Redox Dil


25

Summary

• 100 cm2 LST-GDC co-spray anodes: achieved redox stability but limited <130 W/cm2

-Reactive phase formation, limited film conductivity (SrTiO3 deactivation)

• GE identified methods to improve film conductivity through process opt

-Thermal spray focus shifting to microstructure optimization

• Identified several candidates for scale up: (1) doped SrTiO3 (2) doped SFM

• Goal – scale up 3-4 promising down-selected candidates by Fall

Demonstrate higher power, ceramic anode, metal supported SOFC cells


26

Acknowledgements

• GE Fuel Cells SOFC Team

• GE Global Research Team

• WVU (Dr. Sabolsky, Dr. Liu, Dr. Zondlo, & team)

• Steven Markovich @ DOE/NETL

• Funding provided by the US Department of Energy

through cooperative agreement FE0026169

This material is based upon work supported by the Department of Energy under Award Number FE0026169. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the DOE.


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GE Team:

Rich Hart PI, testing & direction Larry Rosenzweig, Bastiann Korevaar Thermal Spray GRC Dave Dynan Stephen Bancheri, Susan Corah Powder development

Erik Jezek, Becky Northey, Jim Gardner Materials testing, microstructure & degradation Dayna Kinsey, Luc Leblanc, Matt Alinger GE Fuel Cells, scale up Thermal Spray Todd Striker, Andy Shapiro, Simon Gaunt Systems Support

Mike Vallance Echem Model Jae Hyuk Her, Erik Telfeyan, Matt Ravalli Analytical Support

Johanna Wellington, Steve Duclos, GE Management Support Katharine Dovidenko, Wei Cai


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WVU Team

Principle Investigators:

Dr. Xingbo Liua

Dr. Edward M. Sabolskya

Dr. John Zondlob

Research Assistants:

Dr. Tony Thomasa

Laura (He Qi)a

aDepartment of Mechanical and Aerospace Engineering

bDepartment of Chemical Engineering

West Virginia University

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