DEVELOPMENT OF NON-AQUEOUS
ASYMMETRIC HYBRID SUPERCAPACITORS
BASED ON Li-ION INTERCALATED
COMPOUNDS
GUIDE
Dr.D.KALPANA, SCIENTIST,
EEC DIVISION,
CECRI,
KARAIKUDI.
BY
NAKKIRAN.A
INTRODUCTION
WHAT IS A CAPACITOR?
capacitor is a device used for storing charges and energy in its simplest
form.
A capacitor consists of two conducting surfaces separated by an insulating
material ( Dielectric).
PRINCIPLE:
What are Supercapacitors?
Supercapacitors are an advanced version of capacitors with unique
ability to combine energy storage capabilities of batteries and
power storage behavior of capacitor.
Hence fill the gap between batteries and conventional capacitors
such as the electrolyte capacitors in terms of specific energy as
well as specific power.
PROPERTIES OF ENERGY STORAGE
DEVICES
DEVICE
CAPACITORS EDLC
BATTERY
CHARGING TIME
sec m sec
m sec - minute
Hours
DISCHARGE TIME
sec m sec
m sec minute
Minutes months
CYCLE LIFE
106 - 108
106 - 108
200-1000
SPECIFIC POWER
(W/KG)
> 10,000
1000-3000
<500
SPECIFIC ENERGY
( Wh/KG)
<0.01
0.5-5
50-300
TYPES OF SUPERCAPACITORS
1.EC DOUBLE LAYER CAPACITORS
The term electrochemical double layer capacitor is most
commonly used for carbon based double layer capacitors
because of its high capacitance value.
It generally denotes the supercapacitor having non- faradaic
reactions at both electrodes
CARBON SUPERCAPACITOR
2.PSUEDOCAPACITOR OR
ULTRACAPACITOR
In a pseudocapacitor, there are two basic reactions, which
lead to electrochemical cell.
Both occur at the interface between a conductor and an
electrolyte and both benefits form very high specific surface
areas at the electrode.
The first mechanism commonly referred to as charge
separation, which is well documented as non-faradaic
mechanism and is the basis for EDLC.
The second reaction commonly referred to as an oxidation
reduction reaction due faradaic mechanism.
HYBRID CAPACITOR:
Hybrid power system is a new highly reliable
energy storage device. It is a combination of EDLC and a
battery. (eg. C and Li-ion). Hence it is known as capattery
(capacitor battery)
WHY HYBRID?
In supercapacitor two symmetric capacitors are connected in
series and the total capacitance is halved.
1/Ctotal = 1/C + 1/C
Ctotal = C/2.
But in a hybrid supercapacitor, one of the electrodes is
replaced by a battery electrode. So we can get the total
capacitance of the single capacitor electrode with the added
advantage of battery electrode.
Li-CARBON HYBRID SYSTEM
AIM
Development of hybrid power system combining various
power sources with the supercapacitors is the promising field
of research due to its fundamental advantages of both.
Our work focuses on developing a hybrid system combining
Li-ion battery and Carbon based supercapacitor.
We proposed to study the various supercapacitors based on
cathode material such as LiMn2O4, LiCoO2, LiFeP2O7 and
other such materials.
CATHODE MATERIAL
Our work starts with making pure and doped lithium
manganate as suitable candidate for Lithium ion based
supercapacitor system
Why Lithium manganate ?
Spinel LiMn2O4 is of great interest as a cathode
material for lithium ion batteries.
Advantage:
High voltage, low cost and low toxicity
Disadvantage:
Poor cycling behavior because of a fast capacity fading
due to Jahn Teller distortion
JAHN TELLER DISTORTION AND ITS
REMEDY
Average oxidation state of the manganese in LiMn 2O4 is
3.5 and thus any small perturbation influencing the
oxidation state may alter the ratio of Mn 4+ and Mn3+.
When the ratio of Mn3+ increases ,it follows a
disproportionate reaction
2Mn3+
Mn4+ + Mn2+
and causes high solubility of spinel material into the
solution.
Remedy:
Wahihara suggest that partially substituted LiMxMn1-xO4
(M=Co, Cu, Ni, Mn) shows improved cyclability due to the
stronger M-O bonding of octahedron structure in comparison
to that of Mn-O bonding in LiMn2O4.
Hence we studied the both pure and the doped manganate
system
SYNTHESIS OF CATHODE MATERIAL
SOL-GEL PROCESS:
LiCo0.25Cu0.25Ni0.25Mn1.25O4
LiMn2O4
Li2CO3+MnCO3 in Acetic acid
Stirring at 500C
for 30 minutes
Li2CO3+MnCO3+CuCO3+CoCO3+
NiCO3.Ni(OH)3.1.5 H2O in Acetic acid
Addition of 50ml of EtOH
Heating at 800C
for 4 hours
Addition of Ammonia solution(30%)
Addition of 2 X Glycine
Heating until
gel formation
Filtering, Drying and Grinding
1.Heating at 5000C for 12 h
2.Firing at 6500C for 12 h
3.Calcining at 7500C for 12h
Physical characterization
SEM
XRD
FTIR
SCANNING ELECTRON
MICROGRAPHS
LiMn2O4
LiCo0.25Cu0.25Ni0.25Mn1.25O4
X-RAY DIFFRACTION
JCPDS# 35-0782
LiMn2o4:
a= 9.412 A0, b= 8.233 A0, c=
0
4.1002A0, V= 317.73 A 3
LiCo0.25Cu0.25Ni0.25Mn1.25O4:
a= 8.162, b= 7.0844, c= 6.235
0
V= 360.6 A 3
Pristine LiMn2O4 adopts a cubic Fd3m space group
The XRD data does not shows any structural distortion on
doping which is evident when the doping concentration
increases X<0.5
FTIR SPECTROGRAPHS
The 628cm-1 peak is associated with
the symmetric Mn-O stretching
vibration of the MnO6 groups.
The peaks 558, 512 and 418cm-1 are
attributed to bending mode of CoO6
octahedral (558) and Ni2+-O
stretching mode (512&418),
respectively in the doped compound
structure.
ANODE MATERIAL
CNF Carbon Nano Foam
High surface area (1500 m2/g)
Low electrical resistance
No participation in faradaic reactions at the applied voltage
High capacity (100 - 200 F/g)
Unlike AC, CNF combine high surface area with high bulk
density to give large capacitance values
CELL FABRICATION
CONSTITUENTS:
POSITIVE ELECTRODE -
LiMn2O4(80%)
CNF(15%)
NMP(5%)
NEGATIVE ELECTRODE CNF(95%)
NMP(5%)
ELECTROLYTE
1M LiClO4 in EC-PC
SEPARATOR
POLYPROPYLENE
CURRENT COLLECTOR SS
ELECTRODE AREA
1 cm2
GRINDING AND MIXING
COMPLETE SUPERCAPACITOR
AFTER PASTING AND DRYING
COMBINED ELECTRODES
ELECTROCHEMICAL CHARACTERIZATION
1.
2.
3.
Electrochemical Impedance
spectroscopy
Cyclic voltammetry
Galvanostatic charge / Discharge
CYCLIC VOLTAMMETRY
FOR LiMn2O4:
Specific capacitance
(F/g)
FOR LiCo0.25Cu0.25Ni0.25Mn1.25O4 :
= Avg current/scan rate/weight of the
material
Scan rate
1 mV/s
2 mV/s
Pure
34
31
29
Doped
22
20
19
Material
5 mV/s
IMPEDANCE SPECTROSCOPY
9
Doped
Pure
8
7
Z''(Ohm)
5
4
w
C
3
2
1
0
-1
5
z'(Ohm)
10
11
12
13
Impedance parameters
PARAMETERS
RS (Ohm)
Rct (Ohm)
Cdl (mF/g)
PURE
5.128
0.2917
2.98
DOPED
5.043
0.2394
3.14
MATERIAL
CHARGE-DISCHARGE
DOPED
PURE
2.4
2.0
1.8
2.0
1.6
1.4
1.2
Voltage(V)
Voltage(V)
1.6
1.0
0.8
0.6
0.4
0.2
1.2
0.8
0.4
0.0
6300 6350 6400 6450 6500 6550 6600 6650
Time(sec)
900 1000 1100 1200 1300 1400 1500 1600
Time (sec)
FORMULAE USED
Current x Discharge time
Specific Capacitance = Voltage x weight
Current x Voltage
Specific Power =
weight
Current x Voltage x Discharge time
Specific Energy =
weight
RESULTS
PROPERTY
SPECIFIC
CAPACITANCE
(F/g)
SPECIFIC
POWER
(kW/kg)
SPECIFIC
ENERGY
(kWh/kg)
LiMn2O4
15
200
20
LiCo0.25Cu0.25Ni0.25Mn1
.25O4
110
MATERIAL
FUTURE WORK
Finding the cycle life behavior of this capacitor and
variation of properties with cycle life.
Continuing the same work for the LiCoO2 cathode material
prepared by various methods and comparing their results
with the results of LiMn2O4.
THANK YOU
QUERIES ?
