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Title: CitrateNitrate based Combustion Synthesis of Nanocrystalline Multicomponent Oxides for Different App


1
Citrate-Nitrate based Combustion Synthesis of
Nano-crystalline Multi-component Oxides for
Different Applications
H S Maiti
Central Glass Ceramic Research Institute,
Kolkata, India. (Council of Scientific
Industrial Research)
2
Processing techniques for nano- crystalline
materials for different application
  • Sol- gel method
  • Co precipitation technique
  • Physical or Chemical Vapor Deposition
  • Auto combustion method
  • Spray pyrolysis

Importance of auto-combustion / spray pyrolysis
technique
  • Single phase liquid stage synthesis
  • Better homogeneity in the chemical composition
  • Preparation of multicomponent ceramic oxide
    materials
  • Controlled shape, size and morphology of the
    particulates can be produced in a single step by
    spray pyrolysis technique
  • Spray pyrolysis process is easy to scale up

3
Preparation of Functional Ceramics by Auto-
ignition Technique
Metal Nitrates
Citric Acid
Mixed Solution
Foaming / Gas Evolution
Heating / Stirring
Phase pure, Homogene- ous and Ultrafine Powder

Calcination

Further Heating
Glowing Flints
Auto ignition / Ash formation
Gel formation
4
The basic redox reaction that occurs between the
citrate and nitrate ions may be represented as
follows
Single Step Decomposition of a Typical
Citrate-Nitrate Gel
C6H8O7 M (NO3) x MOx NO CO2H2O
5
  • Synthesis of Materials for Two Specific
    Technologies
  • Solid Oxide Fuel Cell
  • Lithium Ion Rechargeable Battery

6
What is Solid Oxide Fuel Cell (SOFC) ?
7
SOFC Stack (Planar Configuration )

8
SOFC Materials and Properties for MEAs (Membrane
Electrode Assemblies)
9
Anode-supported Planar Cells
Single Cells Microstructure
  • Optimum microstructure achieved
  • Porous cathode (LSM)
  • Relatively dense CFL (LSM-YSZ)
  • Dense gas-tight electrolyte (YSZ)
  • Porous anode (Ni-YSZ)

LSM ( 50 µm)
10 cm ? 10 cm ? 1.5 mm
CFL ( 7µm)
Fabricated large numbers of single cells for
stack development
YSZ (10 µm)
Ni -YSZ (1.5 mm)
10
Process Flow Diagram for Synthesizing
Nano-crystalline SOFC - Cathode Materials by
Complex-gel Auto-combustion Method
11
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12
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13
Effect of Precursor Concentration on Thermal
Characteristics of the LSM Gel
14
Particle size and sintering of LSM powders
Densification Vs Sintering temperature of LSM
(La0.84Sr0.16MnO3 ) of different concentration of
the precursor solution
Agglomerated particle size distribution of LSM
Calcined at 750oC
Conductivity at 950oC 125 Scm-1 ( for 92 dense
sample)
15
Optimization of process parameters for the
synthesis of cathode materials by Spray Pyrolysis

16
Versatility of Spray Pyrolysis Technique
Synthesis of ceramic powders
  • Compositions single to
    multicomponent oxides
  • Particle size nanometers
    micrometers
  • Particle morphologies solid soft hollow
    particles

in a single operation unlike other solution
processing routes
Types of Spray Pyrolysis Technique
  • Conventional Aerosol Decomposition (CAD)
  • Salt Assisted Aerosol Decomposition (SAD)
  • Electrospray Pyrolysis
  • Low Pressure Spray Pyrolysis using Filter
    Expansion Aerosol Generator
  • (FEAG)

17
CAD Spray Pyrolysis
18
Existing Spray Pyrolysis Facility at CGCRI
19
Physical Model of Droplet Formation by CAD
Tw (K)
Decomposition
Drying
Evaporation
Precipitation
?sv ?sl
solvent vapor diffusion
Atomization
Co (mol/l)
Hollow particle
solution
Radius of the reactor (cm)
R
r
droplets
solution
precipitation
solvent vapor
?sv ltlt ?sl
Solid particle

Tw (K)
Length of the reactor (cm)
?sv characteristic time for solvent evaporation
?sl characteristic time for solute diffusion
20
Large Scale Production of LSM Powders by
Spray-Pyrolysis
Continuous production of nano crystalline LSM
powders have been achieved by Spray Pyrolysis of
a Citrate-Nitrate Precursor Solution
21
Optimization of Process Parameters for CAD
  • Spray parameters
  • Atomization pressure
  • Feed rate of the precursor solution
  • Flow rate and type of the carrier gas
  • Port opening of the spray nozzle
  • Concentration of the precursor solution
  • Evaporation of the atomized droplet
  • Radius of the atomized droplet
  • Temperature of the liquid droplet

22
Doped lanthanum ferrite - based nano-crystalline
cathode
23
TG and DTA of the LSCF gel using (a) citric
acid, (b) glycine and (c) mixed fuel
c)
  • With citric acid (Fig.a), multistage
    decomposition occurs during the combustion
  • Single stage decomposition results at 170
    0C(Fig. b) with glycine as a fuel
  • Mixed fuel G/C 41 shows the optimum regarding
    single stage decomposition of LSCF-2 precursor
    gel. Mixed fuel nitrate ratio fixed at 0.75
  • Irrespective of the fuel used no further weight
    loss occurs above 4000C

24
Phase analysis by X-ray diffraction (XRD) method
Fig.1 XRD of LSM powder
Fig.2 XRD of LSCF powder
  • For LSM-2
  • 85 phase pure with LaMnO3 and Mn3O4 as a
    secondary phases is obtained before calcination
    (Fig.1a)
  • single phase rhombohedral with 99 phases
    purity is obtained after calcination
    (Fig.1b)
  • The structure of LSCF-1 and LSCF-4 is purely
    rhombohedral
  • LSCF-2 is rhombohedral phase , along with a small
    amount of La2O3.
  • 75-LSCF-2-M SP resembles with that of the LSCF-2
    (Fig.2)
  • The average crystallite sizes for LSCF1, LSCF4
    and LSCF2 are found to be 24, 62 and 19 nm
    respectively

25
Powder Micro-structure Analysis
  • Soft agglomerated particulates forms during LSM
    complex gel combustion in the laboratory (a)
  • Spray pyrolysis of LSM produces agglomerate free
    materials with average particle size about 50 nm
    (b)
  • LSCF-2 synthesized by auto-combustion using
    L-alanine as the fuel, shows agglomerate free
    particulates with average particle size of 70-80
    nm (c)

26
Optimization of process parameters for the
synthesis of cathode materials by modified Spray
Pyrolysis technique
27
Microstructures of 0.2 (M) SP LSM (a) w/o solid
loading (b) with 20 solid loading under
gravity feed
Microstructures of 0.5 (M) SP LSM with 50
solid loading under gravity feed
28
Enhanced Electrochemical Performance of SOFC
Single Cells with Modified Spray Pyrolysed
Cathode Powders
Electrochemical performance of SOFC single cell
Ni-SZ/YSZ/CFL(LSM YSZ)/CL(LSM) CFL and CL
processed by spray pyrolysis technique
Electrochemical performance of SOFC single cell
Ni-SZ/YSZ/CFL(LSM YSZ)/CL(LSM) CFL and CL
processed by modified spray pyrolysis technique
29
Typical Performance of SOFC Single Cells
(Ni-YSZ/YSZ/CGO/LSCF)
1.1 A/cm2
N.B CGO is synthesized by auto-combustion
technique by ammonium ceric nitrate gadolinium
nitrate as precursors
30
Synthesis characterization of doped ceria
based electrolyte by auto combustion technique
31
Optimum process condition for synthesizing doped
ceria by auto-combustion technique
X-ray diffraction pattern of doped ceria a) C/N
0.1 b) C/N 0.3 and c) C/N 0.5
32
TEM micrograph of doped ceria calcined at 600 oC
  • At 500oC, the residual grain boundary resistance
    is completely absent.
  • The capacitance values obtained from the plot
    are a) air 2.05 x 10-11 F b) Ar 2.12x 10-11 F
    c) 3 H2/Ar 2.22x10-11 F

Complex impedance spectra of sintered ceria at
500 oC in air, argon and 3 H2/Ar atmosphere
33
Synthesis characterization of doped lanthanum
molybdate based electrolyte by auto combustion
technique
34
  • Single phase material is produced after
    calcination
  • ? - La2Mo2O9 is pseudocubic in symmetric

X-ray diffraction pattern of doped lanthanum
molybdate a) undoped La2Mo2O9 b) Rietveld
refinement plot of La1.94Ba0.06Mo2O9
  • La1.94Ba0.06Mo2O9 showed conductivity of 1.53 x
    10-4 8.42 x10-2 S/cm at 500 and 800oC
    respectively
  • La2Mo2O9 showed conductivity of 1.2 x 10-4
    5.29 x10-2 S/cm at 500 and 800oC respectively

Temperature dependent electrical conductivity of
doped lanthanum molybdate
35
Characterization of doped lanthanum chromite
based interconnect by auto combustion technique
36
TEM combustion synthesized nano-crystalline doped
LCR
La0.9Ca0.1Cr0.9Al0.1O3 calcined at 7000C
La0.9Ca0.1Cr0.9Mg0.1O3 calcined at 7000C
1µm
Sintered microstructure of La0.9Ca0.1Cr0.9Al0.1O3
Sintered microstructure of La0.9Ca0.1Cr0.9Mg0.1O3
Nano crystalline grains of sintered LCR is
retained after doping of Ca and Al in A
and B site respectively
37
Lithium-ion Battery
ICEPS-2008, Thiruvananthapuram, Nov 26-28, 2008



Fuel Cell Battery Division, CGCRI
38
Lithium-ion Battery
600kW, 370km/h, Jan 06
39
Rechargeable Battery Systems
4.1 V
1.2 V
1.35 V
2.1 V
40
Synthesis of LiCoO2 Cathode Material by Citric
Acid aided Combustion Synthesis
X-ray diffraction pattern of LiCoO2
  • Rhombohedral layered structure LiCoO2 with R3m
    space group
  • Hexagonal grains with grain size of 80-100 nm
  • Rhombohedral layered structure LiCoO2 with R3m
    space group
  • Hexagonal grains with grain size of 80-100 nm

41
FESEM of of combustion synthesized LiCoO2
Hexagonal grains with grain size of 100 nm
are observed
100 nm
Cyclic Voltammetry of LiCoO2 based coin cells
after cycle 1
  • Oxidation peak at 4.0 V
  • Reduction peak at 3.8 V

42
Electrochemical Studies
Galvanostatic charge-discharge of LiCoO2 based
coin cells
Cycling test of LiCoO2 based coin cells at
various current densities
43
Lithium battery activities at CGCRI
  • Indigenization of commercial LiCoO2 powder for
    use in 18650 cell
  • Development of alternate cathodes e.g., LiMn2O4,
    LiFePO4, Li(Co1/3Mn1/3M1/3)O2 M Ni, Fe, Cr,
    Cu
  • Development of alternate anodes e.g., Li4Ti5O12,
    SnO/SnO2, Si/C

Synthesis
2032 coin cell fabrication
1. Combustion 2. Templating 3. Spray Pyrolysis
(large scale) 4. Chemical Vapour Depostion
Electrolyte 1 M LiPF6 in ECDMC 11 Anode Li
metal foil, MCMB, Graphite
Material characterization
Electrochemical characterization
  • Charge-discharge
  • Cyclic Votametry
  • AC Impedance Spectroscopy
  • Cycle Life Testing
  • Galvanostatic Cycling at High Temperature
    (60-80oC)
  • Rate Capability Study
  • Thermal Properties
  • Structure and Phase Analysis
  • Microstructure and Morphology
  • Particle Size and Surface Area
  • Electrical Properties
  • Optical Properties

44
Effect of Advanced Material Processing LiMn2O4 A
Case Study
ICEPS-2008, Thiruvananthapuram, Nov 26-28, 2008



Fuel Cell Battery Division, CGCRI
45
Carbon exo-templating synthesis LiMn2O4
Loading in active carbon matrix
Preparation of Semi-viscous solution
1. LiNO3 2. Mn(ac)2
Alanine
Active carbon
150oC Heat with constant stirring
Semi-viscous Gel
46
Carbon exo-templating synthesis LiMn2O4
Active carbon matrix loaded with precursor gel
Precursor material
Dried at 80oC, 12 hours
Active carbon
Intermediate calcination at 600oC to remove
templete
Product Powder
Final calcination at 800oC
ICEPS-2008, Thiruvananthapuram, Nov 26-28, 2008



Fuel Cell Battery Division, CGCRI
47
Microstructure evolution
CP-LiMn2O4
CET-LiMn2O4
Aggleromerated morphology obtained by
conventional combustion process
Multifaceted morphology obtained by carbon
exotemplating process
ICEPS-2008, Thiruvananthapuram, Nov 26-28, 2008



Fuel Cell Battery Division, CGCRI
48
Electrochemical properties
Comparison of cycleability of LiMn2O4 /Li cell
synthesized by (a) combustion process (CP) and
(b) carbon exo-templating (CET)
Good capacity retention on cycling (CET )
CET-LiMn2O4
Severe capacity fading (Combustion)
CP-LiMn2O4
ICEPS-2008, Thiruvananthapuram, Nov 26-28, 2008



Fuel Cell Battery Division, CGCRI
49
Electrochemical properties
CET-LiMn2O4
CET-LiMn2O4
CP-LiMn2O4
Cyclic voltemmetry
Cycleability test
Sharp and intense peak indicates high
crystallinity and good reversibility of LiMn2O4
powder synthesized by CET method.
CET-LiMn2O4 shows excellent reversibility and
rate capability at high current densities
ICEPS-2008, Thiruvananthapuram, Nov 26-28, 2008



Fuel Cell Battery Division, CGCRI
50
Filter paper templating method
Optical microscope images
Alanine
1. LiNO3 2. Mn(ac)2
150oC Heat with constant stirring
Semi-viscous Gel
ICEPS-2008, Thiruvananthapuram, Nov 26-28, 2008



Fuel Cell Battery Division, CGCRI
51
Filter paper templating Method
Schematic diagram of FPT process
Swelling of fibers
FTP-LiMn2O4
(Necklace type interconnected grains 40-60 nm)
ICEPS-2008, Thiruvananthapuram, Nov 26-28, 2008



Fuel Cell Battery Division, CGCRI
52
Electrochemical properties
FTP-LiMn2O4
Low rate of impedance growth even after 110
cycles indicates high cycle life of the cell (No
manganese dissolution into the electrolyte)
Excellent rate performance with no significant
capacity fading during cycling
53
Microstructure engineering by co-doping
By controlling the dopant amount (Ni and S),
different kind of microstructure can be
tailor-made
Microstructure of pristine LiMn2O4
Spherical
Microstructure of Ni-doped LiMn2O4 oxysulfide
Microstructure of highly Ni-doped LiMn2O4
oxysulfide
Polygon
Octahedron
54
More examples of different co-doped oxysulfides
Fe,S co-doped LiMn2O4
Cu,S co-doped LiMn2O4
Ga,S co-doped LiMn2O4
B,S co-doped LiMn2O4
Microstructure can be engineered by choosing
proper dopant and also their concentration in the
mother matrix
55
Electrochemical performance of Ni-doped
oxysulfide
LiNixMn2-xO4-?S?
Microstructure plays crucial role in
electrochemical performance of the electrode
materials
Poor performance
Pristine LiMn2O4
No capacity fading per cycle
x0.2 Ni doped oxysulfide
LiNixMn2-xO4-?S? shows the best electrochemical
performance
High discharge capacity during cycling 135 mAh/g
x0.4 Ni doped oxysulfide
x0.3 Ni doped oxysulfide
x0.5 Ni doped Oxysulfide
(a) Agglomerated morphology (b) Co-doped
lithium manganese oxysulfide having faceted
microstructure
56
Conclusions
  • Ni and S co-doping has a remarkable effect on
    the microstructure of LiMn2O4
  • Grains having definite geometrical shape may be
    obtained by choosing proper dopants
  • Ni and S co-doped samples show excellent
    electrochemical cycling performance under
    repeated cycling
  • No capacity fading has been observed during
    cycling due to structural stability induced by S
  • 0.4 mol Ni-doped sample shows the best
    electrochemical performance

ICEPS-2008, Thiruvananthapuram, Nov 26-28, 2008



Fuel Cell Battery Division, CGCRI
57
Conclusion
  • Auto-combustion technique is the versatile and
    liquid phase synthesis of the multi-component
    ceramic oxides
  • Spray pyrolysis is the unique semi-continuous
    mode of operation of such multi-component ceramic
    oxides in a single step
  • LSM, LSCF, CGO, La2Mo2O9 , LCR and LiCoO2 have
    been synthesized successfully by auto-combustion
    technique among which optimization of the process
    parameters for LSM and LSCF based cathode
    materials is carried out by spray pyrolysis
    technique
  • As-synthesized powders show 85 phase purity
    whereas 99 of phase purity is achieved after
    calcination both spray pyrolyzed LSCF and LSM
    powder
  • All the materials synthesized either by
    auto-combustion technique or spray pyrolysis
    technique have been characterized and have shown
    reasonably better performance.

58
Acknowledgement
  • Dr. Sukumar Roy
  • Dr. P. Sujatha Devi
  • Dr. A. Chakraborty
  • Dr. R. N. Basu
  • Dr. A. Das Sharma
  • Shri J. Mukhopadhyay
  • Shri S. Basu
  • Dr. S. Mohanty

59
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