1. DEVELOPMENT OF NON-AQUEOUS ASYMMETRIC
HYBRID SUPERCAPACITORS BASED ON Li-ION
INTERCALATED COMPOUNDS
GUIDE
Dr.D.KALPANA, SCIENTIST, BY
EEC DIVISION, NAKKIRAN.A,
CECRI,
KARAIKUDI.

2. An overview of previous presentation
• Introduction
• Hybrid supercapacitors
• Synthesis of LiMn2O4 and the same multidoped
with Ni, Co and Cu
• Physical characterization - XRD, SEM, FTIR
• Cell Fabrication

3. Electrochemical
Characterization
techniques

4. • Cyclic voltammetry
• Galvanostatic charge-discharge
• Electrochemical impedance spectroscopy

5. Cyclic Voltammetry
Before cycles:
LiMn2O4 LiCo0.25Ni0.25Cu0.25Mn1.25O4
0.0010
1mV/s
0.0010 1mV/s
2mV/s
0.0005 2mV/s
5mV/s
5mV/s
0.0005
0.0000
current(A)
0.0000
-0.0005
-0.0005
-0.0010
-0.0010
-0.0015
2000 1000 0 -1000 -2000
2000 1000 0 -1000 -2000
Voltage (mV)
voltage(mV)

6. Cyclic Voltammetry
After 5000 cycles:
LiMn2O4 LiCo0.25Ni0.25Cu0.25Mn1.25O4
0.0010 0.0010
1mV/s 1mV/s
2mV/s 2mV/s
5mV/s 5mV/s
0.0005 0.0005
current(A)
current(A)
0.0000 0.0000
-0.0005 -0.0005
-0.0010 -0.0010
2000 1000 0 -1000 -2000
2000 1000 0 -1000 -2000
voltage(mV)
voltage(mV)

7. Cyclic Voltammetry
Scan rate = 5mV/s
LiMn2O4 LiCo0.25Ni0.25Cu0.25Mn1.25O4
0.0010 before cycles 0.0010
before cycles
after 5000 cycles
after 5000 cycles
0.0005 0.0005
current(A)
0.0000 current(A) 0.0000
-0.0005 -0.0005
-0.0010 -0.0010
-0.0015 -0.0015
2000 1000 0 -1000 -2000 2000 1000 0 -1000 -2000
voltage(mV) voltage(mV)

8. Cyclic Voltammetry
Scan rate = 5mV/s
Before cycles: After 5000 cycles:
LiMn O
2 4 0.0010
0.0010 LiMn2O4
Li(CoNiCu)0.25Mn1.25O4
Li(CoNiCu)0.25Mn1.25O4
0.0005
0.0005
current(A)
current(A)
0.0000
0.0000
-0.0005
-0.0005
-0.0010
-0.0015 -0.0010
2000 1000 0 -1000 -2000 2000 1000 0 -1000 -2000
voltage(mV) voltage(mV)

9. Formula used
Average current
Specific capacitance =
Scan rate x Weight

10. Cyclic Voltammetry
Results
Specific capacitance of
Specific capacitance of LiMn2O4
LiMn1.25Co0.25Ni0.25Cu0.25O4
(F/g)
Condition ( F/g)
1mV/s 2mV/s 5mV/s 1mV/s 2mV/s 5mV/s
Before
34 31 29 22 20 19
cycles
After 5000
27 22 18 18 16 15
cycles

11. Charge-Discharge Profiles of
LiMn2O4
Current density = 500µA/cm2
2.4
2.4
cycle no.2 2.2
2.0 after 5000 cycles
2.0
1.8
1.6
1.6
Voltage(V)
voltage in V
1.4
1.2
1.2
0.8 1.0
0.8
0.4 0.6
0.4
0.0 0.2
0.0
900 1000 1100 1200 1300 1400 1500 1600 700 750 800 850 900 950 1000 1050 1100 1150
Time (sec)
Time in s

12. Charge-Discharge Profiles of
LiCo0.25Ni0.25Cu0.25Mn1.25O4
Current density = 500µA/cm2
2.0 2.0
cycle no.3 after
1.8 1.8 5000 cycles
1.6 1.6
1.4 1.4
Voltage(V)
1.2 1.2
voltage in V
1.0 1.0
0.8 0.8
0.6 0.6
0.4 0.4
0.2 0.2
0.0
6300 6350 6400 6450 6500 6550 6600 6650 450 500 550 600 650 700 750
Time(sec) Time in s

13. Formulae used
Specific Capacitance = Current x Discharge time
Voltage x weight
Current x Voltage
Specific Power = weight
Current x Voltage x Discharge time
Specific Energy =
weight

14. Charge-Discharge results
LiMn2O4 LiMn1.25Co0.25Ni0.25Cu0.25O4
Condition
Specific Specific Specific Specific Specific Specific
capacitance power energy capacitance power energy
F/g kW/kg kWh/kg F/g kW/kg kWh/kg
Before
14.55 200 21.98 5.36 110 5.8
cycles
After 5000
7.85 200 11.83 4.17 110 4.58
cycles

15. Columbic efficiency Vs Cycles
Coulombic efficiency = discharge time/charging time
100
LiMn2O4
Li(CoNiCu)0.25Mn1.25O4
Coulombic efficiency (%)
90
80
70
0 1000 2000 3000 4000 5000

16. Internal resistance Vs Cycles
IR = ∆V/ ∆I
800 LiMn2O4
Li(CoNiCu)0.25Mn1.25O4
Internal resistance(ohm)
700
600
500
400
300
0 1000 2000 3000 4000 5000
No of cycles

17. Specific capacitance Vs Cycles
20
Specific Capacitance (F/g)
16
LiMn2O4
Li(CoNiCu)0.25Mn1.25O
4
12
8
4
0
0 1000 2000 3000 4000 5000
No of cycles

18. Electrochemical Impedance
spectroscopy
Before cycles: After 5000 cycles:
-800
LiMn2O4
-8 LiMn2O4 -700
Li(CoNiCu)0.25Mn1.25O4
Li(CoNiCu)0.25Mn1.25O4
-600
-6
-500
Zim(ohm)
Zim(ohm)
-400
-4
-300
-200
-2
-100
0 0
-200 0 200 400 600 800
4 6 8 10 12 14
Zre(ohm)
Zre(ohm)

19. Impedance results
LiMn2O4 LiMn1.25Co0.25Ni0.25Cu0.25O4
Condition
Rs Rct Cdl Rs Rct Cdl
ohm ohm mF/g ofm ohm mF/g
Before
5.128 0.2917 2.98 5.043 0.2394 3.14
cycles
After 5000
7.829 278 0.195 6.573 122.4 0.59
cycles

20. Structure Vs capacity fading
• The structural stability of a host electrode to the
repeated insertion and extraction of lithium is
undoubtedly one of the key properties for ensuring
that a lithium ion cell operates with good
electrochemical efficiency
• In transition metal oxides, both stability of the
oxygen ion array and minimum displacements of the
transition metal cations in the host are required to
ensure good reversibility.

21. Structure of cubic SPINEL

22. Structural Change
• the cubic symmetry of Li[Mn2]O4(space group
Fd3m), in which the lithium ions occupy tetrahedral
sites and Mn occupy the Octahedral sites
• On cycling the lithium ions occupy octahedral sites
of Mn ion ,So the cubic symmetry of LiMn2O4 is
reduced to tetragonal Li2[Mn2]O4 (space group
F41/ddm)

23. Cubic to tetragonal transition
LiMn2O4 Li2Mn2O4
CUBIC TETRAGONAL
[a=b=c] [a=b=c]

24. • This crystallographic distortion, which results
in a 16% increase in the c/a ratio of the unit
cell parameters
• Average Oxidation state of cubic spinel is 3.5
• Average Oxidation state of tetragonal spinel is
3

25. Jahn Teller distortion
When the ratio of Mn3+ increases ,it follows a
disproportionate reaction
2Mn3+ Mn4+ + Mn2+
Where Mn2+ is an acid-soluble species .It
dissolute into solution. And distrust its
structural integrity during cycling.

26. Remedy
• This multi-doped system maintains the
average oxidation state of Mn ion between
3.5 to 4.
• So JT distortion is reduced to the greater
extend

27. Conclusions
• The faster rate of capacity fading in pure
substance than doped one may be attributed
to the onset of Jahn-Teller distortion
• The above point may be confirmed without
any doubts soon after the arrival of XRD
results for the sample after 5000 cycles.

28. Conclusions
• The low IR in the case of doped substance
is also a strong reason for its better
performance
• The impedance profiles too explain clearly
that doped substance is a better candidate
for supercapacitors than the pure one

29. Conclusions
• With LiMn2O4 we were able to reach a high
voltage of 2.4v, while the highest voltage
that has ever been reported for this system
is 1.8v
• This high voltage may be attributed to the
use of organic electrolyte – 1M LiClO4 in
EC-PC

30. Lithium Cobaltate(LiCoO2)
• Commercially
successful
• The layered structure
of LiCoO2enables
easy diffusion of Li-
ions in and out of the
structure

31. Synthesis Of Cathode Material
• Two cathode materials were synthesized,
i) Pure LiCoO2
ii) LiCoO2 doped with Al - LiCo1-xAlxO2 ( x = 0.2, 0.4,…..0.8 )
• The cathode material was synthesized by soft combustion method
• Compositions were taken on a stoichometric ratio based on following
equations,
• LiNO3 + Co(NO3)2.6H2O LiCoO2 (for pure substance)
• LiNO3 + 0.8Co(NO3)2.6H2O + 0.2Al(NO3)2.9H2O LiCo0.8Al0.2O2
(for doped substance)

32. Composition For Pure Substance
Basis : 0.1 moles(9.8g) of product
Chemical Weight
LiNO3 6.9 g
Co(NO3)2.6H2O 29.1 g
Glycine ( C2H5NO2) 15 g
Distilled Water 100 ml

33. Composition For Doped Substance
Basis : 0.2 moles of product
Chemical Weight
LiNO3 13.8 g
Al(NO3)2.9H2O 15 g
Co(NO3)2.6H2O 46.56 g
Glycine ( C2H5NO2) 30 g
Distilled Water 100 ml

34. The Soft Combustion Process
Weighing of required chemicals
Dissolve in 100ml distilled water
Stir well at 600C
Heat the mixture at 1000C for 8 hours
Product is formed following a soft combustion

35. Thermal Analysis

36. Future Work
• Physical characterization of LiCoO2
• Cell fabrication
• Electrochemical characterization
• Comparison of LiMn2O4 and LiCoO2 using
the available data

37. Thank you

38. Queries?