Effects of Composition and Operating Conditions on the Microstructure and

Performance of LSM-Based SOFC Cathodes

Naima Hilli,1 Celeste E. Cooper,1 Chenxin Deng,1 Andrew Cai,1Zhien Liu,2 Richard Goettler,2 Arthur Heuer,1 & Mark De Guire1

1) Department of Materials Science and Engineering, Case Western Reserve University

2) LG Fuel Cell Systems

U.S. Department of Energy Hydrogen and Fuel Cells Program 2018 Annual Merit Review and Peer Evaluation Meeting

Washington, DC • 13–15 June 2018

Outline• (La1–x Srx)1–y MnO3±δ (lanthanum strontium manganite, LSM)

— effect of Mn excess (A-site deficiency) on long-term performance

• Durability testing ⇒ ASR (area specific resistance) vs. time

• Cathode microstructural changes

• TEM/EDXS (transmission electron microscopy / energy-dispersive x-ray spectroscopy)

• 3DR (3D reconstruction)

• New observations and questions

• Comparison: long-term conventional testing vs. accelerated testing

• Mn distribution and its evolution with time — a clue to degradation?

Cell specifications; testing procedures• Button cells fabricated at LGFCS

• 8YSZ electrolyte • NiO / 8YSZ anode • Cathodes: LSM / 8YSZ

• (La0.85 Sr0.15)0.90 MnO3±δ (LSM 85-90) — 11% Mn excess • (La0.80 Sr0.20)0.95 MnO3±δ (LSM 80-95) — 5% Mn excess • (La0.80 Sr0.20)0.98 MnO3±δ (LSM 80-98) — 2% Mn excess

• Cell testing • Anode: humidified H2, 50 sccm• Cathode: ambient air • Accelerated tests:

1000 °C, 0.760 A cm–2

• Conventional tests: 900 °C, 0.380 A cm–2

• I–V and EIS scans every ~24 or ~48 h

0.100

0.150

0.200

0.250

0.300

0.350

0 100 200 300 400 500 600

LSM 85-90 11% Mn xs

Electrode* ASR (accelerated testing)

LSM 85-90 (11% Mn xs):• Highest ASR overall• Highest rise in ASR

ASR ↓ as Mn excess ↓ LSM 80-98 (2% Mn xs):• Lowest ASR overall• Highest power, 500 h

elec

trod

e AS

R, Ω

cm2

time, h

LSM 80-95 5% Mn xs

LSM 80-98 2% Mn xs

*) total cell DC ASR, minus estimated ASR for 8YSZ substrate @ nominal thickness & DC conductivity

5

Microstructural change after 500 h accelerated testing

LSM 85-90 (11% Mn xs) LSM 80-95 (5% Mn xs) LSM 80-98 (2% Mn xs)

as re

ceiv

ed50

0 h,

acc

el’d

• Coarsening of pores & LSM

• Densification of CCC*

• Highest overall microstructural stability

• Coarsening of pores & LSM

• Densification of CCC*

e’lyte cathode CCC*

*) cathode current collector

0.1

0.15

0.2

0.25

0.3

0.35

0 5 10 15 20 25

0 hrs◆ LSM 85-90 (11% Mn xs)■ LSM 80-95 (5% Mn xs)● LSM 80-98 (2% Mn xs)

active TPB density [ µm–2 ]

elec

trode

ASR

[ Ω

cm2 ]

0 h

68 h

500 h624 h

0 h

0 h

506 h

• As Mn excess ↑, ASR ↓

• As test time ↑:• Active TPB ↓• Total ASR ↑

• Effects on ASR diminish as Mn excess ↓

6

ASR and TPB density: role of Mn excess (accel’d testing)

◆◆

◆

◆

●●

■■■

493 h

201 h

cells tested at 800 oC

as fired 2 kh 8 kh 16 kh

Prior work, normal conditions: TEM/EDXS

1) H.-J. Wang et al., 14th SECA Workshop, Pittsburgh, Pennsylvania, July 2013. 2) H.-J. Wang et al., Metall. Mater. Transactions E: Materials for Energy Systems 1 [3] 263-271 (2014).

At cathode-electrolyte interface* after extended testing:1

• Reduced porosity • Accumulation of Mn2O3 or Mn3O4 2*) Left side of each image

• Cathode densification near cathode-electrolyte interface • Evident after 16 kh/860 oC, but not after 8 kh/860 oC

Prior work, normal conditions: 3DR

Ref.: H.-J. Wang et al., 14th SECA Workshop, Pittsburgh, Pennsylvania, July 2013

9

Phase profiles across cathodes

As-received and 500-h conv’l testing: uniform phase profiles

Porosity gradients, lowest at e’lyte interface

10

as received

LSM 80-95: phase profiles, 0–624 h accel’d testing

624 h accel’d500 h accel’d

5% Mn excess:• Develops porosity

gradient during operation, …

• … denser at cathode/ electrolyte interface

• Not localized at e’lyte

Microstructural evolution during operation

Normal conditions, 8,000–16,000 h: • Loss of porosity

at cathode/electrolyte interface

• Mn oxides:• localized at cathode/

electrolyte interface• increasing with time

Accelerated conditions, ≤ 624 h: • Porosity gradient, lowest

at cathode/electrolyte interface

e’lyte LSM-8YSZ cathode CCC

• As received (0 h)

• MnOx observed sparingly across entire cathode

• 493 h accelerated testing• MnOx near cathode/

e’lyte interface and in LSM cathode current collector (CCC)

11% Mn excess: TEM w/EDXS, 0–493 h accel’d testing

e’lyte LSM-8YSZ cathode CCC

13

500 h

624 h

as received

5% Mn excess: TEM w/EDXS, 0–624 h accel’dtesting

e’lyte LSM-8YSZ cathode CCC

MnOx:• Rarely seen in

cathode• Seen in CCC

Not seen at 5% Mn xs:Densification and MnOxlocalized at cathode/ electrolyte interface

Microstructural evolution during operation

Normal conditions, 8,000–16,000 h: • Loss of porosity

at cathode/electrolyte interface

• Mn oxides:• localized at cathode/

electrolyte interface,• increasing with time

Accelerated conditions, ≤ 624 h: • Porosity gradient, lowest

at cathode/electrolyte interface

• Mn oxides:• localized at cathode/

electrolyte interface,• for Mn excess ≥11%

as receivedMn

La

Sr

72 h 493 h

cathode CCC

15

11% Mn xs: LSM EDXS profiles, 0–493 h accel’d testing

• [Mn] low before testing, • … approached

nominal composition during operation

500 has-received

cation % as received 500 h 624 h

Mn 48 50 52La 40 38 36Sr 11 11 11

LSM 80-95Nominal Composition

Mn

Sr

La

624 h

5% Mn excess: LSM EDXS profiles, 0–624 h accel’d testing

• Uniform YSZ composition across cathodes

• Little change after 493 h

cation % as received 493 hZr-K 79.0 77.0

Y 13.5 14.1Mn 5.2 4.4

11% Mn excess, 8YSZ EDXS profiles, 0–493 h accel’d testing

Zr

Y

as received 493 h

500 h

cation % as received 500 h 624 h

Y 14 14 15Zr 76 76 77.5Mn 4.3 4 4.7

If Mn is “going back into the LSM” during operation, it is not leaving

the YSZ

as-received

8YSZNominal composition

Y

Zr

624 h

5% Mn excess, 8YSZ EDXS profiles, 0–624 h accel’d testing

200–µm electrolyte 100–µm electrolyte

Porosity still lower than other cathodes

No gradients in phase fractions —typical of all as-received cathodes

Significantly lower porosity

LSM 85-90 / 8YSZ (11% Mn excess) — as received

20

100-µmelectrolyte:more MnOx

particles

200-µm electrolyte:larger MnOx

particles

LSM 85-90 / 8YSZ (11% Mn excess) — as received

0 2 4 6 8 10 12 14 16 18 20 22 240

2

4

6

8

10

30

35

40

45

50

55

60

Al Mn Sr Y Zr La

Catio

n %

distance from electrolyte (um)

LSM 85-90nom. comp’n

Mn

La

100-µm e’lyte

Sr

200-µm e’lyte

Mn

La

Sr

LSM 85-90nom. comp’n

LSM 85-90 / 8YSZ (11% Mn excess) — as received

as received LSM 85-90 (100-µm e’lyte) LSM 80-95 LSM 80-98 Cathode D

sample volume (µm3) 5,400 6,300 4,100 6,840

volume fraction (%)

porosity 23 29 28 31YSZ 35 33 37 34LSM 41 38 35 35

Total TPB (µm-2) 20.6 14 22 18.4Active TPB (µm-2) 19.4 13 20 17

Summary: cathode microstructures, as received (3DR)

Testing of LSM 85-90 cathodes on 100-µm electrolytes: in progressporosity is low;

TPB density is relatively high; many small Mn oxide particles;

Net effect on ASR: TBD

Summary• ASR decreases with Mn excess (A-site deficiency) from 11% to 2% —

why?

• Mn oxides: not predictive of ASR or degradation rate

• A local probe of pO2? • A reservoir for Mn?

• Effects of densification at cathode/CCC interface?

• Mn distribution and its evolution with time — a clue to degradation?

• Analysis of EIS results — in progress

• Role of pO2 — focus of new project

Acknowledgments

• Funding: DoE SOFC Core Technology Program (DE-FE0023476)

• Program managers: Dr. Shailesh Vora, Dr. Patcharin Burke (NETL)

• Mirko Antloga (CWRU)

Disclaimer: This research is based in part upon work supported by an agency of the United States Government.Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

• For 2018, prior results not previously presented:

• Conventional test results

• Trends in Rp, Rs, Rtot (EIS vs. durability testing)

• Rp, Rs, Rtot vs. time (CeCe’s thesis) — compare to ASR from durability testing?

• Does higher Relectrolyte (thicker; same material) have more effect on ASR and degradation rate than just the higher resistance itself?

200–µm electrolytelower porosity, smaller pores

100–µm electrolytemore & larger pores

LSM 85-90 / 8YSZ (11% Mn excess) — as received

electrolyte cathode CCC electrolyte cathode CCC

Cathode DLSM 80-98 (C)

LSM 85-90 (A) (thin e’lyte) LSM 80-95 (B)

Vol% LSM 85-90 (thin) LSM 80-95 (B) LSM 80-98 (C) Cathode Dporosity 23 29 28 31

YSZ 35 33 37 34LSM 41 38 35 35

100–µm electrolyte

Vol% LSM 85-90 LSM 80-95 LSM 80-98 Cathode Dporosity 17 29 28 31

YSZ 41 33 37 34LSM 41 38 35 35

11% Mn excess

5% Mn excess 2% Mn excess

All cells showed uniform phase profiles as received

Phase profiles, as received (3DR)

31

Phase profiles across cathode after 500 h accel’d testing (3DR)

All three cathodes developed slight porosity gradients after 500 h of accelerated testing,

with lowest porosity at cathode-electrolyte interface

LSM 85-90

LSM 80-98

LSM 80-95

32

Gen A Gen B Gen C

As reduced

493 h accel test

As received

500h Acceltest

624 hrsAccel test As received

500h Acceltest

sample volume (µm3) 4350 4525 6300 5096 4550 4100 5012

volume fraction (%)

porosity 17 18 29 25 25 28 25YSZ 41 43 33 35 37 37 37LSM 41 38 38 40 38 35 38

particle diameter (μm)

porosity 0.2 0.42 0.4 0.5 0.5 0.3 0.4YSZ 0.5 0.46 0.5 0.5 0.5 0.3 0.5LSM 0.6 0.6 0.6 0.7 0.7 0.5 0.7

tortuosity

porosity 2.0 1.6 1.5 1.7 1.4 1.7 1.7YSZ 1.5 1.3 1.6 1.7 1.5 1.8 1.8LSM 1.3 1.4 1.4 1.4 1.4 1.6 1.6

normalized surface area

(µm–1)

porosity 26 14 16 13 13 21 14

YSZ 12 13 13 12 11 18 13LSM 10 9.9 9 8 8 13 8

Total TPB (µm-2) 17 5.9 14 15 11 22 11

Active TPB (µm-2) 10 5.1 13 13 10 20 10

3D calculation: comparison Gen A, B and C

LSM profiles

LSM 80-98 & 8YSZ EDXS profiles, 500 h accel’d testing

0 2 4 6 8 10 12 14 16 180

2

4

6

8

10

30

35

40

45

50

55

60

Al-K Mn-K Ni-K Sr-K Y-K Zr-K La-K

Catio

n %

distance from electrolyte interface (µm)

8YSZ profiles

Likewise at 2% Mn excess: • Mn level in LSM matches nominal

composition after 500 h accel’d testing• If Mn is “going back into the LSM”

during operation, it is not leaving the YSZ

Mn

La

Sr

0 2 4 6 8 10 12 140

5

10

15

65

70

75

80

85

90

Al-K Si-K Mn-K Ni-K Sr-K Y-K Zr-K La-K

Catio

n %

distance from electrolyte interface (µm)

Zr

Y

Cathode D, as rec’d: microstructure near e’lyte

• Uniform microstructure across cathode• No gradients in phase fractions • LSM matches nominal composition• YSZ contains 4–5 cat% Mn (typical)

• No MnOx observed near electrolyte nor inside cathode

Cathode D, as rec’d: microstructure near CCC

• MnOx not seen inside the cathode nor near CCC interface

• MnOx is observed inside the CCC (red arrows)

A – B – C – D comparison: Electrode* ASR (accel’d testing)

ASR ↓ as Mn excess ↓(A → B → C)

elec

trod

e AS

R, Ω

cm2

time, h

*) total cell DC ASR, minus estimated ASR for 8YSZ substrate @ nominal thickness & DC conductivity

LSM 85-90 (11% Mn xs):• Highest ASR overall• Highest rise in ASR

LSM 80-98 (2% Mn xs):• Lowest ASR overall• Highest power, 500 h

LSM 85-90 (A; 11% Mn xs)

LSM 80-95 (B; 5% Mn xs)

LSM 80-98 (C; 2% Mn xs)

LSM 85–90 (A), as rec’d 200–µm electrolyte 100–µm electrolytesample volume (µm3) 4,350 5,400

volume fraction (%)

porosity 17 23YSZ 41 35LSM 41 41

particle diameter (μm)

porosity 0.2 0.3YSZ 0.5 0.4LSM 0.6 0.6

tortuosityporosity 2.0 1.6

YSZ 1.5 1.6LSM 1.3 1.4

normalized surface area

(µm–1)

porosity 26 21YSZ 12 10LSM 10 9.5

total TPB (µm–2) 17.1 20.6active TPB (µm–2) 10.3 19.4

LSM 85-90 / 8YSZ (A) — as received

as received LSM 85-90 (A) (200-µm e’lyte) LSM 80-95 (B) LSM 80-98 (C) Cathode D

sample volume (µm3) 4,350 6,300 4,100 6,840

volume fraction (%)

porosity 17 29 28 31YSZ 41 33 37 34LSM 41 38 35 35

particle diameter (μm)

porosity 0.2 0.4 0.3 0.4YSZ 0.5 0.5 0.3 0.3LSM 0.6 0.6 0.5 0.6

tortuosityporosity 2.0 1.5 1.7 1.5

YSZ 1.5 1.6 1.8 1.7LSM 1.3 1.4 1.6 1.4

normalized surface area

(µm–1)

porosity 26 16 21 16YSZ 12 13 18 17LSM 10 9 13 9

Total TPB (µm-2) 17 14 22 18.4Active TPB (µm-2) 10 13 20 17

Summary: cathode microstructures, as received (3DR)

0 2 4 6 8 10 12 14 16 18 20 22 240

2

4

6

8

10

30

35

40

45

50

55

60

Al Mn Sr Y Zr La

Catio

n %

distance from electrolyte (um)

LSM 85-90Nominal Composition

Mn

La

• Uniform LSM composition across the cathode composition A Thin electrolyte (as received)

8YSZNominal composition

Y

Zr

• Uniform 8YSZ composition across the cathode composition C • ~4.5 cat% Mn dissolved in 8YSZ

0 2 4 6 8 10 12 14 16 18 20 220

5

10

15

65

70

75

80

85

90

Al Mn Sr Y Zr La

Cat

ion

%

distance from electrolyte um

TEM w/EDXS of bulk 8YSZ composition

• Uniform YSZ composition across cathodes • 4–5 cat% Mn

42

Al Si Mn Ni Sr Y Zr LaCation % 0.6 2.8 4.4 0.3 0.1 14.1 77.0 0.7

~4.4 cation % Mn is found to dissolve in the 8YSZ

LSM 80-95 (B) durability testing: reproducibility

44

0 hrs

500 hrs

June 2016 July 2015

Two cells, accel’d conditions, 500 h

45

specimen 1 specimen 2porosity 27 vol% 28 vol%

YSZ 36 vol% 37 vol%LSM 37 vol% 36 vol%

total TPB 27.4 µm–2 21.7 µm–2

active TPB 24.2 µm–2 20.0 µm–2

LSM 80-98 (C) as received, two specimens

Reproducibility of 3D reconstruction data

specimen 1 specimen 2

Phase fractions & TPB

Phase profiles

standard deviations avg. microstructural params.: 0–5%

TPB: ~15%

Phase profiles at cathode/CCC interface (3DR)500 h accel’d testingas received

LSM 85-9011% Mn xs

LSM 80-955% Mn xs

LSM 80-982% Mn xs

A – B – C comparison: cathode-CCC interface (500 h accel’d testing)

In LSM 85-90 (A) and LSM 80-98 (C), at cathode-CCC interface: • Densification (bottom plot)

Distance (µm)

Volu

me

frac

tion

(%)

Cathode –CCC interface

YSZ

LSM

Pore

A – B – C comparison: porosity and TPB density

Vs. LSM 85-90 (A) and 80-98 (C), LSM 80-95 (B) shows:• Less pore coarsening and loss of pore area• Stabler TPB (total and active)

LSM 85-90; 11% Mn xs LSM 80-95; 5% Mn xs LSM 80-98; 2% Mn xs

as rec’d 493h accel as rec’d 500h accel 624h accel as rec’d 500h accel

sample volume, µm3 4350 4525 6300 5096 4550 4100 5012porosity, volume % 17 18 29 25 25 28 25pore diameter, μm 0.23 0.42 0.38 0.5 0.46 0.28 0.44

pore surface area, µm–1 26 14 16 13 13 21 14total TPB, µm–2 17.1 5.9 14.5 14.8 11 21.7 11.1

active TPB, µm–2 10.3 5.1 13.0 12.5 10 20.0 10.2

• Fabricated at LGFCS

• Cell details:

• 8YSZ electrolyte, 32 mm dia.

• NiO-8YSZ anode (60:40 wt%)

• Cathodes: A-site deficient LSM + 8YSZ (50:50 wt%)

• Comp’n A: (La0.85 Sr0.15)0.90 MnO3±δ(LSM 85-90)

• Comp’n B: (La0.80 Sr0.15)0.95 MnO3±δ (LSM 80-95) • Comp’n C: (La0.80 Sr0.15)0.98 MnO3±δ (LSM 80-98)

• Electrodes: screen printed, 9.5 mm dia., fired separately

Procedures: button cell specifications

F.W. Poulsen, Solid State Ionics 129 (2000) pp. 145 –162

1000 °C

Our observed trend in electrode ASR vs. A/B ratio is opposite of electrical conductivity predicted by defect chemistry modeling.

Pre-test protocol: temperature parametric study

-0.16

-0.14

-0.12

-0.1

-0.08

-0.06

-0.04

-0.02

00.001 0.01 0.1 1 10 100 1000 10000 100000

Z”

Frequency (Hz)

800C(initial)

850C(initial)

900C(initial)

51

cathode

anode

LSM 80-95 (comp’n B), conventional conditions, t = 0

Representative V-I & P-I sweeps, 0–624 h

LSM 80-95 (B), accel’d testing

Representative Bode plots, 0–624 h

LSM 80-95 (B), accel’d testing

Representative Nyquist plots, 24–400 h

54

0 hrs

500 hrs500 hrs

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

00 0.1 0.2 0.3 0.4 0.5 0.6 0.7

-Z"

Z'

Nyquist Plot24 hrs200 hrs300 hrs400 hrs

ASRs, 200h ASRp, 200h

ASR200h

from simple equivalent circuit model (Rs, Rp, Cp)

LSM 80-95 (B), accel’d testing

Cathode B: 500-hr Conventional Test

0

0.2

0.4

0.6

0.8

1

0

0.2

0.4

0.6

0.8

1

0 100 200 300 400 500 600

ASR

(Ω-c

m²)

Volta

ge (V

)

Time (hours)

Durability Testing

VoltageASR

0-24hr: 6.2%

24-165hr: -21.6%

165-506hr: 15.2%

55

Cathode B: 500-hr Conventional Test-0.16

-0.14

-0.12

-0.1

-0.08

-0.06

-0.04

-0.02

00.001 0.01 0.1 1 10 100 1000 10000 100000

Z"

Frequency (Hz)

Bode Plot0 hours

24 hours

43 hours

70 hours

98 hours

114 hours

139 hours

165 hours

189 hours

207 hours

233 hours

258 hours

304 hours

331 hours

357 hours

375 hours

422 hours

449 hours

478 hours

500 hours56

Cathode B: 500-hr Conventional Test

57

-0.16

-0.14

-0.12

-0.1

-0.08

-0.06

-0.04

-0.02

00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Z''

Z'

Nyquist Plot0 hr

24 hr

43 hr

70 hr

98 hr

114 hr

139 hr

165 hr

189 hr

207 hr

233 hr

258 hr

304 hr

331 hr

357 HR

375 hr

422 hr

449 hr

478 hr

500 hr

58

specimen 1 specimen 2Sample Volume (µm3) 4350 4100

Cathode composition C (LSM80-98 / 8YSZ)

Test condition As received Average Std. dev’n % dev’n

Volume Fraction (%)

Porosity 27.3 27.9 27.6 0.37 1.4%

YSZ 36.1 36.8 36.5 0.52 1.4%

LSM 36.6 35.3 35.9 0.90 2.5%

Particle Diameter

(μm)

Porosity 0.26 0.28 0.27 0.01 5.2%

YSZ 0.32 0.32 0.32 0.00 0.00%

LSM 0.49 0.46 0.48 0.02 4.5%

Tortuosity

Porosity 1.66 1.77 1.72 0.08 4.5%

YSZ 1.93 1.86 1.90 0.05 2.6%

LSM 1.73 1.64 1.69 0.06 3.8%

Normalized Surface Area

(µm–1)

Porosity 23.0 21.3 22.1 1.21 5.5%

YSZ 18.6 18.5 18.6 0.08 0.46%

LSM 12.3 13.1 12.7 0.54 4.2%

Total TPB (µm-2) 27.4 21.7 24.6 4.0 16%Active TPB (µm-2) 24.2 20.0 22.1 3.0 14%

Active TPB (%) 88.3 92.1 90.0 2.6 3.0%

Average microstructural parameters: std. dev’ns

Gen Aas received 200 h 493 h

sample volume (µm3) ≈ 4350 ≈ 4620 ≈ 4525

volume fraction (%)porosity 17 17 18.4

YSZ 42 41 43.2LSM 41 42 38.4

particle diameter (μm)

porosity 0.2 0.34 0.42YSZ 0.5 0.6 0.46LSM 0.6 0.7 0.6

tortuosityporosity 2 1.7 1.6

YSZ 1.5 1.43 1.3LSM 1.3 1.35 1.4

normalized surface area

(µm–1)

porosity 26 17.4 14.2YSZ 12 10 13LSM 10 7.6 9.88

Total TPB (µm-2) 17.1 9.6 5.86Active TPB (µm-2) 10.3 8.2 5.13

A – B comparison: 3DR

In contrast to LSM 85-90 (A), LSM 80-95 (B) shows:• Pore refinement (!?) and increasing area and tortuosity• Stabler TPB (total and active)

A – B – C comparison: 3DR

Vs. LSM 85-90 (A) and 80-98 (C), LSM 80-95 (B) shows:• Less pore coarsening and loss of pore area• Stabler TPB (total and active)

Gen A Gen B Gen C

As received

493h Acceltest

As received

500h Acceltest

624 hrsAccel test As received

500h Acceltest

sample volume (µm3) 4350 4525 6300 5096 4550 4100 5012

volume fraction (%)

porosity 17 18 29 25 25 28 25YSZ 41 43 33 35 37 37 37LSM 41 38 38 40 38 35 38

particle diameter (μm)

porosity 0.23 0.42 0.38 0.5 0.46 0.28 0.44YSZ 0.52 0.46 0.45 0.5 0.51 0.32 0.46LSM 0.59 0.61 0.65 0.7 0.72 0.26 0.71

normalized surface area

(µm–1)

porosity 26 14 16 13 13 21 14

YSZ 12 13 13 12 11 18 13LSM 10 10 9 8 8 13 8

Total TPB (µm-2) 17.1 5.9 14.5 14.8 11 21.7 11.1

Active TPB (µm-2) 10.3 5.1 13.0 12.5 10 20.0 10.2

0 hrs

500 hrs

◆ LSM 85-90 (A)◼ LSM 80-95 (B)● LSM 80-98 (C)

◆

●●

493 h 201 h

0 h

68 h

500 h624 h

0 h

0 h506 h

active TPB density [ µm–2 ]

elec

trode

ASR

[ Ω

cm2 ]

◆

◆

◆● ●

• As Mn excess , ASR (A → B → C)

• As test t :• Active TPB • Total ASR • Effects

diminish as Mnexcess (A → B → C)

62

A – B – C comparison: ASR and TPB density

reproducibility: ASR [ Ω cm2 ], 0 h: ± 0.08 (A); ± 0.03 (B)active TPB density [ µm–2 ], 0 h: ± 3.0 (C)

◼ ◼◼

Chart1

electrode ASR [Ω cm^(–2)]10.311.58.19999999999999935.099999999999999613.0112.471022.110.180.231000000000000010.147999999999999960.302999999999999990.3130.176749999999999990.204999999999999990.220.145999999999999990.16400000000000001

accel

A cellsB cellsC cells

0 h0 h0 h0 h0 h10 h, accel68 h, accel213 h, accel493 h, accel201 h,accel0 h0 h0 h0 h34 h, accel275 h, accel500 h, accel624 h, accel0 h0 h0 h0 h< 500 h, accel< 500 h, accel506 h, accel

total TPB density [µm^(–2)]17.112.55.99.614.58.214.811.027.421.711.1

active TPB density [µm^(–2)]10.311.55.18.213.07.7

Mark De Guire: Mark De Guire:After the first 275 h of testing, this cell gave another ~200 of high and erratic ASR. The low TPB mightbe associated with the last phase of the test. 12.510.024.220.010.2

ASR [Ω cm^(–2)] (electrodes)0.2540.1170.2080.3460.2300.2600.1480.3740.3130.3030.1430.1720.2080.1840.1570.1980.2050.2200.1460.164

ASR [Ω cm^(–2)]0.4540.3170.4080.5460.4300.4600.3480.5740.5130.5030.2430.2720.3080.2840.2570.2980.3050.3200.2460.264

ASR [Ω cm^(–2)] (electrolyte)0.2000.2000.2000.2000.2000.2000.2000.2000.2000.2000.1000.1000.1000.1000.1000.1000.1000.1000.1000.1000.1000.1000.1000.1000.100

test ID1_2015 04 081_2015 04 111_2015 05 141_2015 07 091_2015 11 031_2015 04 081_2015 04 111_2015 07 091_2015 05 141_2015 11 032016_03 072_2016 04 162_2015_07 312_2016_06 082_2016 03 072_2016 04 162015_07 312016_06 083_2016 07 223_2016 07 22

average [Ω cm^(–2)]0.2310.177

std dev [Ω cm^(–2)]0.0830.027

std dev %35.8%15.3%

data for plot

active TPB density [µm^(–2)]10.311.58.25.113.0112.471022.110.18

electrode ASR [Ω cm^(–2)]0.2310.1480.3030.3130.176750.2050.220.1460.164

electrode ASR [Ω cm^(–2)]10.311.58.19999999999999935.09999999999999960.231000000000000010.147999999999999960.302999999999999990.313

electrode ASR [Ω cm^(–2)]10.311.58.19999999999999935.099999999999999613.0112.471022.110.180.231000000000000010.147999999999999960.302999999999999990.3130.176749999999999990.204999999999999990.220.145999999999999990.16400000000000001

Slide Number 1Slide Number 2Slide Number 3Slide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Microstructural evolution during operationSlide Number 12Slide Number 13Microstructural evolution during operationSlide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Slide Number 22Slide Number 23AcknowledgmentsSlide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29Slide Number 30Slide Number 31Slide Number 32Slide Number 33Slide Number 34Slide Number 35Slide Number 36Slide Number 37Slide Number 38Slide Number 39Slide Number 40Slide Number 41Slide Number 42Slide Number 43Slide Number 44Slide Number 45Slide Number 46Slide Number 47Slide Number 48Slide Number 49Slide Number 50Pre-test protocol: temperature parametric studySlide Number 52Slide Number 53Slide Number 54Cathode B: 500-hr Conventional TestCathode B: 500-hr Conventional TestCathode B: 500-hr Conventional TestSlide Number 58Slide Number 59Slide Number 60Slide Number 61Slide Number 62