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,

An overview of previous presentations

Introduction Hybrid supercapacitors Synthesis of LiMn2O4 and the same multidoped with

Ni, Co and Cu Physical characterization - XRD, SEM, FTIR Cell Fabrication Electrochemical characterizations Comparison of their performances

Study of supercapacitors

Having LiCo1-xAlxO2 as cathodes

(where x=0,0.2,0.4 and 0.6)

Lithium Cobaltate(LiCoO2)

Commercially successful

The layered structure of LiCoO2 enables easy diffusion of Li-ions in and out of the structure

Why Aluminum

There has recently been considerable interest in Al-doping of lithium intercalation oxides.

Al substitution of the transition-metal cation has been shown theoretically and experimentally to increase the cell voltage.

Some other advantages of Al are that it is light, non-toxic, and inexpensive

Advantage

The similarity of Al and Co ions in these lithium metal oxides makes Al an attractive choice for doping

The end members, a-LiAlO2 and LiCoO2, have the same crystal structure, layered a-NaFeO2 and the metal ions are close in size.

These similarities remove the complications of phase transitions and lattice strain when varying doping content.

Synthesis Of Cathode Material

Two cathode materials synthesized are, i) Pure LiCoO2

ii) LiCoO2 doped with Al - LiCo1-xAlxO2 ( x = 0.2, 0.4,0.6 )

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 + (1-x) Co(NO3)2.6H2O + xAl(NO3)2.9H2O LiCo1-xAlxO2 (for doped substance)

Composition of precursors required for synthesis

Basis : 0.2 moles of product

PrecursorWeight of the material

X=0 X=0.2 X=0.4 X=0.6

LiNO3 13.8g 13.8 g 13.8g 13.8

Al(NO3)2.9H2O - 15 g 30g 45g

Co(NO3)2.6H2O 58.2g 46.56 g 34.92g 23.28g

Glycine(C2H5NO2) 30g 30 g 30g 30g

Distilled Water 100ml 100 ml 100ml 100ml

X= Fraction of Aluminium

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

Physical Characterization

Thermal Analysis X-Ray Diffraction FTIR

Thermal Analysis

TGA is used to find the optimum temperature ranges for drying a sample to remove the moisture and impurities from it.

In DTA phase transitions or chemical reactions are followed through observation of heat absorbed or liberated.

TGA Curves

0 200 400 600 800 1000 1200 14000.4

0.5

0.6

0.7

0.8

0.9

1.0

Weig

ht

fracti

on

Temperature ( 0C)

LiCoO2

LiCo0.8

Al0.2

O2

LiCo0.6

Al0.4

O2

LiCo0.4

Al0.6

O2

DTA Curves

0 200 400 600 800 1000 1200-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Tem

pera

ture

dif

fere

nce(

0 C)

Temperature(0C)

LiCoO2

LiCo0.8

Al0.2

O2

LiCo0.6

Al0.4

O2

LiCo0.4

Al0.6

O2

The initial weight drop from 300C-1500C is due to moisture removal from the sample.

the subsequent weight loss from 1500C to 3000Ccorresponds to elimination of organic compounds from samples.

Next weight drop in the temperature range of 3000C-5000C is formed as a result of the reaction of unreacted precursors to give the final product.

The stabilization temperature for these samples mostly lay after 8000C.

So the samples are heated at 8000C for 4 hours.

TGA Curves

FTIR Curves

500 1000 1500 2000 2500 3000 3500

0

20

40

60

80

100

% T

ran

sm

itta

nce

Wave numbers(cm-1)

LiCoO2

LiCo0.8

Al0.2

O2

LiCo0.6

Al0.4

O2

LiCo0.4

Al0.6

O2

These are the FTIR spectroscopes of LiCoO2, LiCo0.8Al0.2O2, LiCo0.6Al0.4O2, and LiCo0.4Al0.6O2 respectively

For high level of Al substitution, the broadening of the infrared peaks can be interpreted as an increase in CoO6 distortion due to the incorporation of Al3+ in the Co3+ site.

XRD Patterns

10 20 30 40 50 60 70 80 90 100

LiCoO2

LiCo0.8

Al0.2

O2

LiCo0.6

Al0.4

O2

LiCo0.4

Al0.6

O2

(20

1)

(11

3)

(11

0)

(10

8)

(10

7)

(10

5)(1

04

)

(01

2)(0

06

)(1

01

)

(00

3)

2 theta

All samples are single phase and have the α-NaFeO2 structure (space group R3m).

Miller indices (hkl) are indexed in the hexagonal setting.

No impurity phase was detected in the XRD patterns of LiAlyCo1−yO2

On Al doping, the (108) peak shifts towards lower 2θ and the (110) peak shifts towards higher 2θ value

64 66 68

(110)

(108)

LiCoO2

LiCo0.8

Al0.2

O2

LiCo0.6

Al0.4

O2

LiCo0.4

Al0.6

O2

2 theta

XRD Patterns

Electrochemical Characterizations

Cyclic Voltammetry Electrochemical Impedance Spectroscopy Galvanostatic Charge/Discharge

CV of LiCoO2/CNF before cycles

2000 1000 0 -1000 -2000

-0.0008

-0.0006

-0.0004

-0.0002

0.0000

0.0002

0.0004

Cu

rren

t(A

)

Voltage(mV)

1mV/s 2mV/s 5mV/s

1500 1000 500 0 -500 -1000 -1500

-0.0004

-0.0002

0.0000

0.0002

Cu

rren

t(A

)

Voltage(mV)

1mV/s 2mV/s 5mV/s

CV of LiCoO2/CNF after 500 cycles

1500 1000 500 0 -500 -1000 -1500

-0.0006

-0.0004

-0.0002

0.0000

0.0002

0.0004

Cu

rren

t(A

)

Voltage(mV)

1mV/s2mV/s5mV/s

CV of LiCo0.8Al0.2O2/CNF before cycles

1500 1000 500 0 -500 -1000 -1500-0.0002

-0.0001

0.0000

0.0001

0.0002

Cu

rren

t(A

)

Voltage(mV)

1mV/s 2mV/s5mV/s

CV of LiCo0.8Al0.2O2/CNF after 500 cycles

1500 1000 500 0 -500 -1000 -1500-0.00015

-0.00010

-0.00005

0.00000

0.00005

0.00010

0.00015

Cu

rren

t(A

)

Voltage(mV)

1mV/s 2mV/s 5mV/s

CV of LiCo0.6Al0.4O2/CNF before cycles

2000 1000 0 -1000 -2000-0.0006

-0.0004

-0.0002

0.0000

0.0002

0.0004

0.0006

Cu

rren

t(A

)

Voltage(mV)

1mV/s 2mV/s 5mV/s

CV of LiCo0.6Al0.4O2/CNF after 500 cycles

1500 1000 500 0 -500 -1000 -1500

-0.0004

-0.0002

0.0000

0.0002

0.0004

Cu

rren

t(A

)

Voltage(mV)

1mV/s2mV/s5mV/s

CV of LiCo0.4Al0.6O2/CNF before cycles

1500 1000 500 0 -500 -1000 -1500-0.00010

-0.00005

0.00000

0.00005

0.00010

Cu

rren

t(A

)

Voltage(mV)

1mV/s2mV/s

CV of LiCo0.4Al0.6O2/CNF after 500 cycles

Composition

Scan rate

5mV/s 2mV/s 1mV/s

Before cycles

0 15.93 18.75 20.09

0.2 11.6 15.25 16.3

0.4 21.74 26.93 27.61

0.6 6.1 7.63 8.3

After cycles

0 4.113 5.29 11.95

0.2 8.274 10.33 12.93

0.4 16.225 19.74 21.51

0.6 - 5.1 6.4

Specific capacitance (F/g) from CV

0 20 40 60 80 1000

-20

-40

-60

-80

ZIm(O

hm

)

ZRe

(Ohm)

LiCoO2

LiCo0.8

Al0.2

O2

LiCo0.6

Al0.4

O2

LiCo0.4

Al0.6

O2

Impedance Spectroscopy – Before Cycles

0 50 100 150 200 2500

-50

-100

-150

-200

-250

ZIm(O

hm

)

ZRe

(Ohm)

LiCoO2

LiCo0.8

Al0.2

O2

LiCo0.6

Al0.4

O2

LiCo0.4

Al0.6

O2

Impedance Spectroscopy – After 500 Cycles

Property

x

Rs

Ohm

Cdl

mF

Before cycles

0 3.747 0.6194

0.2 2.392 0.5518

0.4 4.551 0.5491

0.6 5.649 0.6328

After cycles

0 4.721 0.6567

0.2 6.253 0.5778

0.4 4.782 0.621

0.6 6.211 0.711

Results of Impedance Spectroscopy

350 400 450 500 550 6000.0

0.4

0.8

1.2

1.6

2.0

Volta

ge(V

)

Time(s)

5600 5610 5620 5630 5640 56500.0

0.7

1.4

2.1

Vol

tage

(V)

Time(s)

Galvanostatic Charge-Discharge behaviour of LiCoO2/CNF

First cycle 500th cycle

Galvanostatic Charge-Discharge behaviour of LiCo0.8Al0.2O2/CNF

26 28 30 32 34 36 38 40 42

0.0

0.8

1.6

Volta

ge(V

)

Time(s)1337 1338 1339 1340 1341 1342 1343 1344

0.0

0.4

0.8

1.2

1.6

2.0

Volta

ge(V

)

Time(s)First cycle 500th cycle

Galvanostatic Charge-Discharge behaviour of LiCo0.6Al0.4O2/CNF

600 650 700 750 800 850 9000.0

0.4

0.8

1.2

1.6

2.0

Volta

ge(V

)

Time(s)9120 9140 9160 9180 9200

0.0

0.4

0.8

1.2

1.6

2.0

Volta

ge(v

)

Time(s)First cycle 500th cycle

Galvanostatic Charge-Discharge behaviour of LiCo0.4Al0.6O2/CNF

105 110 115 120 125 130 135 140 1450.0

0.4

0.8

1.2

1.6

2.0

Volta

ge(V

)

Time(s)

11732 11736 11740 11744 11748 117520.0

0.4

0.8

1.2

1.6

2.0

Volta

ge(V

)

Time(s)First cycle 500th cycle

Results of Galvanostatic Charge-Discharge Analysis

Composition

Properties

Specific capacitanc

e(F/g)

Power density(kW/kg)

Energy density(kWh/kg)

Before cycles

0 11.17 312.5 12.41

0.2 0.415 303.03 0.44

0.4 11.41 333.3 12.68

0.6 1.53 322.58 1.075

After cycles

0 1.8 312.5 2.01

0.2 0.303 303.03 0.336

0.4 3.83 333.33 4.25

0.6 0.88 322.58 0.986

Conclusion

LiCoO2 is a good cathode material for hybrid supercapacitor since it is having specific capacitance of 11 F/g.

In the doped cathode materials, LiCo0.6Al0.4O2 is having good capacitance and cycle behaviour.

Thank You

Queries?