Download 2007年中華民國陶業研究學會會員大會論文格式

Stack Tests of Metal-Supported Plasma-Sprayed SOFC
*Chun-Huang Tsai1, Chang-Sing Hwang1, Chun-Liang Chang1, Sheng-Fu Yang1, Ming-Hsiu Wu1, Cheng-Yun Fu1,
Chang-Shiang Yang1, Szu-Han Wu2, Hung-Hsiang Lin2, Wei-Hong Shiu2
1
Physics Division, Institute of Nuclear Energy Research, Lungtan, Taoyuan 32546, Taiwan, ROC
2
Nuclear Fuels and Materials Division, Institute of Nuclear Energy Research, Lungtan, Taoyuan 32546, Taiwan, ROC
Abstract
This paper presents performance and long-term stability results of metal-supported solid oxide fuel cell (MS-SOFC)
assembled stacks. The MS-SOFC with six-layer structure consisting of porous nickel-molybdenum as an metal-support,
an LSCM (La0.75Sr0.25Cr0.5Mn0.5O3) interlayer, a nano-structured Ce0.55La0.45O3 (LDC)/Ni as an anode, LDC as an anode
interlayer, La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM) as an electrolyte, 50wt%SDC/50wt%SSC as a cathode interlayer and
25wt%SDC/75wt%SSC as a cathode current collector are prepared by atmospheric plasma spraying. The assembled
single cell stack shows remarkable electric output power of 39 and 27.4 W with an effective electrode area of 81 cm2 at
750°C and 700°C. The long-term stability test of the single cell stack shows a degradation rate of about 0.77 % kh−1 at the
test conditions of 400 mA cm−2 constant current density and 700°C. Furthermore, a 25-cell stack is assembled to evaluate
the power performance and it showed a stack power of 829.8 W at 19.85 V and 740 °C. Results demonstrate the success
of APS technology for fabricating high performance metal-supported and LSGM based ITSOFCs.
Keywords: solid oxide fuel cell, atmospheric plasma spraying, nano-structure, Metal-Supported,
Stack
1. Introduction
instance, the manufactures of coatings to improve wear
Solid oxide fuel cells (SOFCs) are very promising
resistance and mechanical properties [4]. This technology
electrochemical energy conversion devices because they
utilizes high temperature plasma flame created by
have high efficiencies and emit low amounts of pollutants.
high-voltage electrodes in the plasma torch to partially or
The recent research in solid oxide fuel cells has been
fully melt injected particles that traverse the plasma jet and
aimed at lowering the operating temperature without
are deposited on a substrate [5]. Comparing with other
reducing the power density. By decreasing the operating
existing processes such as chemical vapor deposition,
temperature of SOFC to around 700°C, many advantages
sol–gel method, tape-casting, screen-printing and physical
are expected. In particular, metal alloy could be used for
vapor deposition for fabricating SOFC cells [6–14],
the material of cell support, separator and stacking
atmospheric plasma spraying is a fast sintering process, it
modules, which would reduce the SOFC manufacturing
allows reducing the interaction between layers of SOFC
cost. Toward lowering operation temperatures, there is a
cells that can be induced during conventional high
tendency to
temperature
shift ceramic-supported
fuel
cells to
sintering
processes,
for
instance,
the
metal-supported fuel cells due to the potential benefits of
interaction between LSGM electrolyte layer and Ni in the
low cost, high strength, better workability, good thermal
anode layer [15]. In addition to high material deposition
conductivity and quicker start-up [1–3].
Plasma spray
rates, APS processes can easily control the component
processing is well established and proven technology in
composition and microstructure through variation of spray
widespread industrial use for a variety of applications, for
parameters, hence, plasma spraying process has thus
appeared as a promising candidate for inexpensive and fast
SDC and SSC-C (SSC with ~15wt% carbon pore former)
cell production, and attracted much attention [16-18].
that were deposited on the porous Ni-Mo substrate by
Plasma spray processes also show strong potential to
atmospheric plasma spraying process. Porous Ni-Mo
enable
of
substrates were fabricated by sintering processes. A
metal-supported fuel cells on porous metallic substrates.
substrate slurry was firstly prepared by mixing nickel
The LSGM material is good candidate of electrolyte for
powders of 90~150μm, molybdenum powers with particle
ITSOFC [15,18]. To establish the reduced temperature and
sizes in 1~5 μm and PVA binder. Then the slurry was
high power density solid oxide fuel cells, this material is
poured into a mold, pressed and dried to form a green
adopted to form the electrolyte of our developed
sheet. This green sheet was sintered at a temperature 1350°
metal-supported SOFC. The challenge to produce a dense,
C for 6 h in a reducing atmosphere to form a porous
crack-free and high conductive LSGM electrolyte is
Ni-Mo substrate with ~8 wt% Mo. This home-made
overcome here so that all the ceramic functional layers,
porous Ni-Mo substrate with 1.0 mm in thickness and 10
including anode, electrolyte and cathode layers, are
cm × 10 cm in size was chosen as a support. The porosity
deposited sequentially on home-made porous Ni-Mo
about 30% of the substrate was measured by the
substrates by atmospheric plasma spraying processes. In
Archimedes method. The permeability of home–made
this article, the metal supported cell produced by
Ni-Mo porous substrate is around 2 Darcy. The average
atmospheric plasma spraying with LSGM electrolyte layer
thermal expansion coefficient around 14.8 × 10-6 °C
was explored and evaluated the cell performance with
Ni-Mo substrate was measured from room temperature to
single cell and 25-cells stack.
800 °C by Netzsch DIL 402 C dilatometer. After finishing
the
sequential
multi-layer
depositions
-1
of
all functional layers including anode, electrolyte and
2. EXPERIMENTAL
2.1 Apparatus
cathode layers that were coated in sequence to construct
metal-supported solid oxide fuel cells, the prepared cell
The robotic APS system primarily consists of a DC
was heated and pressed in air for 4 h at 850°C and 500 g
plasma spray gun (Model TriplexProTM 200, Sulzer
cm-2 pressure to relax the stresses and to improve the
Metco) that generates a high temperature plasma flame
adhesions between coated layers.
under atmospheric condition, a robot (FANUC Robot ARC
Mate 120iB) that holding plasma spray gun to scan
substrate, a powder feeder for delivering plasma spray-able
powders, a cooling system for the torch, a heater for
preheating the substrate, an IR detector for measuring the
temperature of the substrate and a fast CCD camera to
observe trajectories of particles in the plasma flame. Fig. 1
schematically depicts the set-up of our atmospheric plasma
spraying. Other details of experimental apparatus and
Fig. 1 Schematic drawing of atmospheric plasma spray
typical plasma spraying parameters are given in other
(APS) system.
published papers [19, 20].
2.2 Substrate and Cell preparation
Fig.
2
shows
the
commercially
available
agglomerated powders of LSCM, LDC-NiO, LDC, LSGM,
min-1 for sealing process. A weight about 30 kg was loaded
on the top of stack for better sealing and contact. The
hydrogen was then fed into the stack for anode reduction.
After reduction for several hours, the performance of the
stack was tested with a fuel mixture of hydrogen (80 vol%)
and nitrogen (20 vol%) is fed to the anode at 1000 ml
min-1 flow rate and the air oxidizer is fed to the cathode at
Fig. 2
SEM photos of powders: (a) LSCM, (b)
2000 ml min-1 flow rate. Prodigit 3356 DC electronic load
LDC-NiO, (c) LDC, (d) LSGM (e) SSC-C and (f) SDC
is applied for the power measurement. The assembled
used to fabricate metal-supported SOFCs.
25-cell stack shown in Fig. 4 was located in an electric
furnace with a temperature controller. The similar sealing
process and equipment was applied for the power
measurement of the prepared stack.
Fig. 3 the 3D arrangement of components used in
single cell stack measurement configuration.
2.3 Stack development
measurement
and
performance
The electric performances of prepared cells are
Fig. 4 Assembled stack composed of 25
metal-supported solid oxide fuel cells.
measured by the SOFC measurement system located in our
metal-supported SOFC (MSC) and the cell frame in Fig. 3
3. Results and Discussion
3.1 Performances and Long Term Stability of
MSC single cell stack
are welded together by laser. The stacks are sealed to each
The current-voltage (I-V) and current-power (I-P)
other by home-made glass-ceramic sealing materials that
curve of the single cell stack at 750 and 700 °C are shown
are not shown in Fig. 3, which form electrically isolating
in Fig. 5. The MSC single cell stack with effective
layers. Crofer 22 material is applied for making cell frames,
electrode area of 81 cm2 shows the open circuit voltages
anode plates and cathode plates. The LSM coating made
(OCVs) are 1.09 and 1.11 V and the remarkable electric
by atmospheric plasma spraying is applied for avoiding the
output power of 39 and 27.4 W at 750°C and 700°C. The
chromium poison from contacts. The current collectors
output power of 39 W is obtained at a cell potential of 0.68
were by means of nickel and silver meshes at anode and
V at 750°C when the H2 flow rate is 9.8 mL min-1 cm-2 and
cathode. Following assembly, the stack was placed in a
the air flow rate is 24.7 mL min-1 cm-2. Its fuel utilization
furnace and heated to 820°C with a heating rate of 1°C
efficiency at 57.06 A is 54.3%, and the conversion
institute. Fig. 3 gives the 3D arrangement of components
used in single cell stack measurement configuration. The
efficiency (LHV) is 29.5%. From these results, the single
25-cell stack are shown in Fig. 7. Using the anode gas
cell stack has shown a promising performance.
containing a mixture of hydrogen fuel and nitrogen gas as
Fig. 6 shows the long-term operation of the single
-1
-1
well as the cathode gas containing only air oxidizer, the
cell stack operated with 800 ml min H2+200 ml min N2
tested stack can deliver an output power of 829.8 W at
and 2000 ml min-1 air at current density of 400 mA cm-2
about 39 % fuel utilization, 0.794 V and 740 °C. The flow
and 700°C for about 2000 hours. During the long term
rates of hydrogen fuel and nitrogen gas are set at 20 L
operation, the measured voltage starts from 733 mV and
min−1 and 5 L min−1 respectively. The flow rate of air
ends at 723 mV. The estimated degradation rate is
oxidizer is set at 50 L min−1. Fig. 8 gives the OCVs and
approximately 0.77% kh-1. It indicates that the MSC stack
power densities at 0.794 V of the cells in the 25-cell stack
with the APS LSM protective coatings on corfer22
operated at 740 °C. The OCV of each cell is larger than
interconnector have a very good durability performance at
1.05 V. This implies that all electrolyte layers of 25
700°C.
metal-supported solid oxide fuel cells prepared by the APS
processes are dense enough to be gas tight. Experimental
data of the tested stack demonstrate the success of APS
technology
for
metal-supported
fabricating
and
LSGM
high
performance
based
intermediate
temperature solid oxide fuel cells.
Fig. 5 the I-V-P curves of single cell stack with
hydrogen at 700 and 750℃.
Fig. 7 Voltage and power versus current of the 25-cell
stack.
Fig. 6 The durability test result of single cell stack
with hydrogen at 400mAcm-2 current density and 700℃.
3.2 Performances of MSC 25-cell stack
Furthermore, a stack composed of 25 metal-supported
solid oxide fuel cells (10 x 10 cm2) with the same layer
structure as the tested single cell stack was successfully
Fig. 8 OCVs and power densities at 0.794 V of the cells in
assembled. The voltage and power versus current of this
the 25-cell stack operated at 740 °C.
4. Conclusions
[9] L.R. Pederson, P. Singh, X.D. Zhou, Vacuum, 80 ,
The 10 x 10 cm2 LSGM based metal-supported solid
1066–1083 (2006).
oxide fuel cells fabricated by atmospheric plasma spraying
[10] J.L. Young, T.H. Etsell, Solid State Ionics 135 (2000)
method show promising results. The developed solid oxide
457–462.
fuel cell with a Ni-Mo metal substrate, a micron-scale
[11] S. Zha, Y. Zhang, M. Liu, Solid State Ionics, 176,
structured LSCM diffusion barrier layer,a nanostructured
25–31 (2005).
LDC-Ni
cathode
[12] D. Simwonis, H. Thulen, F.J. Dias, A. Naoumidis, D.
interlayer and a 25wt%SDC-75wt%SSC cathode current
Stover, J. Mater. Process. Technol, 92–93, 107–115
collector has been tested for 2000 hours to get the
(1999).
durability results. The experimental results demonstrate
[13] J. Van herle, R. Ihringer, R. Vasquez Cavieres, L.
the developed cell has an encouraging durability with an
Constantin, O. Bucheli, J. Eur.Ceram. Soc,
estimated degradation rate of ~0.77% kh-1 at test
1855–1859 (2001).
anode,
a
50wt%SDC-50wt%SSC
conditions of 400 mA cm
-2
21,
current density and 700 °C
[14] N. Jordan, W. Assenmacher, S. Uhlenbruck, V.A.C.
temperature. This developed cell is able to deliver the
Haanappel, H.P. Buchkremer, D. Stöver, W. Mader, Solid
remarkable power densities of 39 and 27.4 W at 750°C and
State Ionics, 179, 919–923 (2008).
700°C. The developed stack with 25 such cells can also
[15] X. Zhang, S. Ohara, H. Okawa, R. Maric, T. Fukui,
deliver a remarkable output power of 829.8 W at 39 % fuel
Solid State Ionics, 139, 145–152 (2001).
utilization, 19.85V and 740 °C. Each cell in this 25-cell
[16] R. Hui, Z. Wang, O. Kesler, L. Rose, J. Jankovic,
stack has an OCV value larger than 1.05 V showing the
S.Yick, R. Maric, D. Ghosh, J. Power Sources, 170,
high density of the electrolyte.
308–323 (2007).
[17] R. Henne, J. Therm. Spray Technol, Vol.16, (3)
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1
1
蔡俊煌 , 黃振興 , 張鈞量 , 楊昇府 ,吳明修 , 傅正允 ,
摘要
2
本文介紹金屬支撐型固體氧化物燃料電池
（MS-SOFC）組裝電池堆的性能和長期穩定性結果。具
有六層結構的金屬固體氧化物燃料電池，以多孔鎳鉬合
金作為載體，LSCM（La0.75Sr0.25Cr0.5Mn0.5O3）作為中間層，
具納米結構 Ce0.55La0.45O3（ LDC）/ Ni 作為陽極，LDC 作
為陽極隔離層，La0.8Sr0.2Ga0.8Mg0.2O（LSGM）
3
作為電解質，
50wt％SDC / 50wt％SSC 作為陰極複合層，25wt％SDC /
75wt％SSC 作為陰極集電層。此電池組裝的單電池堆在
750℃和 700℃溫度下發電功率為 39 和 27.4 瓦特，電池
2
-2
有效發電面積為 81cm 。在 400mA cm 定電流密度和 700
-1
℃的長時間測試條件下，其性能衰退率約 0.77％kh 。另
外， 由 25 片金屬支撐型固體氧化物燃料電池組裝而成
的電池堆電性測試評估顯示，在溫度 740℃，電壓 19.85
伏特下，電池堆功率達 830 瓦特。實驗結果證明利用大
氣電漿噴塗技術成功製備出以 LSGM 為電解質，具高性
能的金屬支撐型中低溫固態氧化物燃料電池。
關鍵字：大氣電漿噴塗、固態氧化物燃料電池、金屬支
撐、奈米結構、電池堆