Investigation on Microstructure and Conductivity of ZEBRA Battery Cathode Tannaz Javadi Dr. Anthony Petric Dr. Gianluigi Botton 1
Feb 23, 2016
Investigation on
Microstructure and
Conductivity
of ZEBRA Battery Cathode
Tannaz Javadi
Dr. Anthony PetricDr. Gianluigi Botton
MTLS 702
1
1- Microstructure of the cathode
2- Thermodynamic modeling of ZEBRA cycling
3- Conductivity measurement of the liquid electrolyte with temperature.
4- Effect of adding additives on liquid electrolyte conductivity
Contents:
2
Anode (-): Na metal
Cathode (+): Transition metal chloride
+ Excess metal
ElectrolyteSolid electrolyte: β“-Alumina (≥ 0.2 Ω -1cm-1 at 260 ˚C)
Liquid electrolyte: NaAlCl4 (0.6 Ω -1cm-1 at 250 ˚C)
J.L . Sudworth, J. Pow. Sour., 100 (2001)
ZEBRA battery 1978 ZEolite Battery for Research in Africa
FeCl2 NiCl2
Ni- Cu composite Current Collector
2.58 V @ 300 ˚C2.35 V @ 250 ˚C
(200- 300 ˚C) (200- 400 ˚C)
3
Na
NaCl+Ni
NiCl2
NaAlCl4
Liquid electrolyte
+ve Current Collector
Charged area
Discharged area
Reaction front
-ve Cell case
Solid ceramic electrolyte
Na ionsrout
e
Introduction:
Na = Na+ + e- Negative electrode
NiCl2 + 2Na+ + 2 e- = Ni + 2NaCl Positive electrode
2NaCl + Ni NiCl2 + 2Na E = 2.58 V @ 300 ˚C
Charge
Discharge
Anhydrous NiCl2 and Na Loading in discharged state
Micron size
4
Cycling reactions:
The net reaction:
Cell 1: charge=48.3 Ah at 325 ˚C, discharge= 40.8 Ah at 295 ˚C.
Cell 3: charge=Similar to Cell1, discharge= 38 Ah at 295 ˚C.
Cell 763: First 12 cycles similar to Cell 3, discharge= 26.2 Ah at 295 ˚C.
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1- The cathode-β” alumina interface 2- The cross section of the cathode from β”- alumina to current collector
Vacuum Distillation: Heated up to 450˚C, under vacuum for 4 h.
2345678910
11
12
13
1415
2
β“-Al2O3Current collector
1
5
Experimental materials:
Sample preparation:
10 µ
A: NaCl,B: Ni, C: NaAlCl4
D: NiCl2
E: Na6FeCl82 µ
E
D
A
C
B
1 µ
D
Charged cell
FIB cross section
Discharged cell
6
SEM & FIB Images:
Room temperature microstructure deviates from real phases
present during operation at high temperature
FactSage database are appropriate
for modeling ZEBRA chemistry
Examination of cell reaction during cycling
Phase changes during cooling
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Thermodynamic modeling
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Thermodynamic modeling
charging Discharging
Overcharge (L +NiCl2)
Increase in solubility of NiCl2 in molten salt
Ni grain growth
Tannaz Javadi, Anthony Petric, J. Electrochem. Soc., V.158, Issue 6, p. A700-A704, (2011).
SEM micrographs show that there are Ni particles that are isolated.
In these cases charge transfer may have problems
AB
B
C
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Incentive to improve electrolyte conductivity
Molten salts have relatively low resistivity
Reactive nature of Sodium Chloroaluminate to moisture
Volatile
The U-shaped capillary
High cell constant
Conductance cell design
The U-shaped capillary
The dip-type capillary design
The non-capillary type
High cell constant
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Potentiostat and Frequency Analyzer Nyquist plot
Conductivity measurement of NaAlCl4
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Tungsten wire
Conductivity Cell
Measuring cell constant using different concentration KCl at different temperatures
Concentration(Molarity)
Conductivity (K (Ω-1cm-1))
18 ˚C 25 ˚C
1 0.09783 0.11134
0.1 0.011166 0.012856
0.01 0.0012205 0.0014087
R = Resistance (Ω)
ρ = Resistivity (Ω.cm)
l = length
A = area
≈ 400 cm-1
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Conductivity Cell Calibration
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Con
duct
ivity
(Ω-1cm
-1)
T (˚C)
Conductivity of pure NaAlCl4 with temperature
Results
0 0.05 0.1 0.15 0.2
-4.99999999999992E-05
7.92822838630025E-19
5.00000000000008E-05
0.000100000000000001
0.000150000000000001
0.000200000000000001
0.000250000000000001
0.000300000000000001 Pure NaAlCl4
I (A
mps
)
E (Volts)
Electronic conductivity of pure NaAlCl4 with temperature
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170 300 4300.35
0.45
0.55
0.65
0.75
0.85
0.95
1.05
Pure NaAlCl45(mol%)NbCl520(mol%)NbCl530(mol%)NbCl540(mol%)NbCl5
ResultsC
ondu
ctiv
ity (Ω
-1cm
-1)
T (˚C)
The conductivity of different percentage of NbCl5 in NaAlCl4
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log
10 (a
ctiv
ity)
Alpha
NbCl5 + <a> Bi
NbCl3 (S)
NbCl4 (S) Nb3Cl8 (S)NbCl4 (S)
Bi (mol)
Thermodynamic modeling; Possible phases at different Mole fraction Bi
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Con
duct
ivity
(Ω-1cm
-1)
T (˚C)
Results Electrical Conductivity with Temp.
140 190 240 290 340 390 440 490 5400.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
Pure NaAlCl430%NbCl5+0 mol Bi30%NbCl5+0.2 mol Bi30%NbCl5+0.5 mol Bi
Ele
ctric
al c
ondu
ctiv
ity (Ω
-1cm
-1)
Bi (mole %) Effect of different concentrations of Bi added to 30% NbCl5 and NaAlCl4 mixtures at 300 ˚C.
Results Electrical Conductivity NaAlCl4+NbCl5+Bi (300 ˚C)
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Electrical conductivity (Ω
-1cm-1)
Log
10 (a
ctiv
ity)
(Mole)BiPhases present at different concentrations of Bi in the mixture at 300 ˚C and their effect on conductivity
Results Possible phases at different Mole fraction Bi
I (A
mps
)
E (volts)
The I-E curve for different mixtures of NbCl5 + Bi +NaAlCl4. The scan rate is 1 mV/s and the range of voltage is 0-0.2V vs. Reference.
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
-0.0001
-0.00005
0
0.00005
0.0001
0.00015
0.0002
0.00025
0.00030.9 mole Bi+ 30 % NbCl5
0.75 mole Bi+30% NbCl5
0.5 mole Bi+30%NbCl5
0.2 mole Bi+30%NbCl5
Pure NaAlCl4
Results Electronic conductivity (300 ˚C)
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Conductivity (Ω-1cm-1)Pure NaAlCl4 0.03830%NbCl5+0.2 mole Bi 0.5330%NbCl5+0.5 mole Bi 0.57230%NbCl5+0.75 mole Bi 0.5730%NbCl5+0.9 mole Bi 0.50
1- Thermodynamic modelling predicts the presence of different phases at operating temperature and confirmed the SEM results.
2- SEM micrographs from ZEBRA cell cathode reveal the existence of isolated Ni particles that may not contribute to the cycling reaction as they are all surrounded by merely ionic conductors.
3- A special conductivity cell with high cell constant was designed to
measure the conductivity of hygroscopic and volatile NaAlCl4.
4- The effect of different additives on conductivity of the liquid electrolyte was examined by using EIS.
5- Among different additives, 30 % NbCl5 + 0.2 mole Bi shows the best
conductivity.6- The conductivity of the liquid electrolyte approximately doubles
between 190 and 490 ˚C.7- The electronic conductivity of the mixtures were measured by using
DC technique. Results show the presence of electronic conductivity in electrolyte by adding dopants.
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Summery
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• Dr. Anthony Petric• Dr. Gianluigi Botton• Dr. Gary Purdy• Dr. Gu Xu• CCEM staff• Jim Garrett
Acknowledgement
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Thank you