2 section. technological development (mcfc) material used now anode: ni-cr, ni-al cathode: li x ni...
TRANSCRIPT
2 Section
Technological development(MCFC)
Technological development(MCFC)
Material used now ANODE: Ni-Cr, Ni-Al CATHODE: LixNi(1-x)O ELECTROLYTE: Li2CO3/K2CO3
Na2CO3
MATRIX: -LiAlO2
ANODE CC: Ni/AISI310S/Ni CATHODE CC: AISI310S SEP. PLATE (AA): AISI310S SEP. PLATE (NAA): AISI310S/Al
Materials actually used in MCFC are suitable to have high electrochemical performance and long operation time
In view of Fuel Cell market, it is still possible to think to improve materials to obtain higher performance, longer operation time and low cost
Technological development(MCFC)
Technological development(Electrochemical Performance)
Reaction Rate Loss mainly depends on materials used for anode and cathode
(catalyst property)
Resistance Loss mainly depends on ionic resistance of electrolyte and electronic resistance of anode, cathode,
metallic components included corrosion layers
Gas Transport Loss mainly depends on anode and cathode
materials morfology
Reaction Rate Loss mainly depends on materials used for anode and cathode
(catalyst property)
Reaction Rate Loss Electrochemical properties of Ni (for H2
oxidation reaction), and NiO (for O2 reduction reaction) are very high
However, limited improvements should be possible by addition of catalyst in standard anode, cathode materials (Cost?, CO use?)
Technological development(Electrochemical Performance)
Resistance Loss Use of thin electrolyte layer decrease ionic
resistance (gas separation problem) Use of electrolyte with low ionic resistance:
Li2CO3/Na2CO3 has lower ionic resistance than Li2CO3/K2CO3
Use of materials for metallic components with higher corrosion resistance (thin corrosion layer with high electrical conductivity corrosion products)
Technological development(Electrochemical Performance)
Gas Transport Loss Porosity, surface area of anode and cathode
are suitable to obtain low gas transport loss (bi-modal morfology of cathode)
However improvement should be possible with higher surface area (nanomaterials?)
Technological development(Electrochemical Performance)
Technological development(Operation time)
Cathode dissolution LixNi(1-x)O has not completely chemical stability
in working conditions Precipitation of Ni in Matrix can produce a
direct electronic contact between anode and cathode
Internal current flow means electrical performance decay
Use of more chemical stable materials should be useful (catalyst for cathodic reaction, high electronic conductivity)
CATHODE (+)
ANODE (-)
MATRIX
Ni++
NiO+CO2 Ni++ + CO3--
Ni++ +H2+ CO3-- Ni + H2O+CO2
Technological development(Operation time)
e
Technological development(Operation time)
Metallic components corrosion Metallic components corrosion means
mechanical property degradation
Anode current collector section OM analysis. a) Before operation b) After operation:it is possible to see Ni coating degradation (lower corrosion protection), and carburisation of AISI310S grains (lower mechanical property)
a)
b)
Technological development(Operation time)
Porous components micro-structural degradation Porosity, pore size distribution, surface area and morfology
of anode and cathode material change in time due to axial load and sintering (Anode)
These changes on electrodes materials mean electrochemical performance degradation (P=0)
Porosity, pore size distribution, surface area and morfology of matrix material could change in time due to -LiAlO2 to -LiAlO2 phase transition (gas composition)
These changes on matrix material mean gas separation property degradation (increase of pore size, matrix not totally filled by electrolyte)
Technological development(Operation time)
Electrolyte loss Electrolyte loss depends on metallic
materials corrosion, vapour phase in gas stream
When electrolyte quantity is not enough to have totally filled matrix, direct contact of H2 and O2 will be possible (electrical performance degradation)
Lab level test(Performance)
Single cell test Single cell is useful to test
electrical performance in lab scale MCFC
Chronogram of single cell voltage/current characterisation.
0
0,2
0,4
0,6
0,8
1
1,2
Time
Vo
ltag
e (V
)
0
5
10
15
Cu
rren
t (A
)
Voltage
Current
Characterisation Voltage and Power/Current Density
0
200
400
600
800
1000
1200
0 50 100 150 200 250 300
Current density (mA/cm2)
Vo
lta
ge
(V
)
0
5
10
15
20
Po
we
r (
W)
Voltage single cell 1
Voltage single cell 2
Power density single cell 1
Power density single cell 2
Lab level test(Performance)
Activation Pol.
Ohmic Pol.
Concentration Pol.
Lab level test(Performance)
Gas analysis In-out single cell gas analysis are performed to
check gas utilisation and possible gas reaction through matrix
Lab level test(Operation time)
Single cell Voltage, Voltage iR free, iR trend
0
100
200
300
400
500
600
700
800
900
1000
1100
0 500 1000 1500 2000 2500 3000 3500 4000
Time(h)
Vo
lta
ge
(m
V)
0
2
4
6
8
10
12
14
16
18
20
iR (
mO
hm
)
V (5,5 A)
IR (mOhm)Matrix filling level control
Lab level test(Operation time)
Lab stack test Lab size stack is useful to test
electrical performance of more cells in stack configuration
10
11
12
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14
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18
19
0 50 100 150 200 250 300 350 400 450 500
Time [unit]
Vo
lta
ge
[V
]
0
10
20
30
40
50
60
70
80
Cu
rre
nt
[A]
Voltage [V]
Current [A]
Lab level test(Operation time)
Post test analysis SEM-EDS
ANODE, CATHODE, MATRIX SEM ANODE, CATHODE, MATRIX SEM ANALYSISANALYSIS
(Micro- structural change) (Micro- structural change)
Lab level test(Operation time)
ANODE, CATHODE, MATRIX PORE SIZE ANALYSISANODE, CATHODE, MATRIX PORE SIZE ANALYSIS
(Micro- structural change) (Micro- structural change)
Lab level test(Operation time)
Porosity reduction
Pore size distribution
change
Lab level test(Operation time)
Crogiolo di allumina
Elettrodo di Nichel porosoimpregnato di carbonati Li/K
Campione metallico(spessore circa 0.3 mm)
Elettrodo di Nichel porosoimpregnato con carbonati Li/K
Caricomeccanico
Camera del forno
TermocoppiaIngresso gas
ANODIC GAS: H2 / CO2 (80/20)
CATHODIC GAS: Air / CO2
T = 650 °C
GAS INThermocouple
Fournace
Metal sample (thickness: 0.3 mm)
Alumina crucible
Porous Ni electrode filled with Li/K carbonate
Porous Ni electrode filled with Li/K carbonate
Pressure load
0
50
100
150
200
250
300
350
400
450
500
0 3000 6000 9000 12000
Corrosion Time (hours)
No
co
rro
ded
sec
tio
n (
mic
ron
s)
Serie1
Trend to 40.000 hours
Lab level test(Operation time)
Material analysis
Lab level test(Cost reduction)
Tape CastingMaterial analysis
Drying
Material analysis
Binder burn out and sintering
Lab level test(Cost reduction)
RAW MATERIALS ANALYSISRAW MATERIALS ANALYSIS
SEMXRD
GRANULOMETRY
Lab level test(Cost reduction)
Use of cheaper raw materials
Conclusion
Fuel cell is an electrochemical device that converts energy of a chemical reaction into electricity without any kind of combustion and with high conversion capability and low environmental emissions.
Molten Carbonate Fuel Cells don’t use expensive catalytic material (Platinum); it can works using CO (reformed natural gas); Operating temperature (650 °C) permit use of stainless steel for metallic components fabrication
MCFC market entry depends on operating life increase and cost reduction. Both points strongly depend on materials used in Fuel Cell preparation