effects of composition and operating conditions on the ... · effects of composition and operating...
TRANSCRIPT
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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
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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
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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
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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
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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
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• 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
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9
Phase profiles across cathodes
As-received and 500-h conv’l testing: uniform phase profiles
Porosity gradients, lowest at e’lyte interface
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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
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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
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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
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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%
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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
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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
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• 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
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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
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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
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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
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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
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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.
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• 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?
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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
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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)
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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
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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%
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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
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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
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• 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.
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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