DEVELOPMENT OF NON-AQUEOUS DEVELOPMENT OF NON-AQUEOUS ASYMMETRIC HYBRID SUPERCAPACITORS ASYMMETRIC HYBRID SUPERCAPACITORS

BASED ON Li-ION INTERCALATED BASED ON Li-ION INTERCALATED COMPOUNDSCOMPOUNDS

BY

NAKKIRAN.A

GUIDE

Dr.D.KALPANA, SCIENTIST,

EEC DIVISION,

CECRI,

KARAIKUDI.

INTRODUCTIONINTRODUCTION

WHAT IS A CAPACITOR?WHAT IS A CAPACITOR?

capacitor is a device used for storing charges and energy in its simplest capacitor is a device used for storing charges and energy in its simplest form. form.

A capacitor consists of two conducting surfaces separated by an insulating A capacitor consists of two conducting surfaces separated by an insulating material ( Dielectric).material ( Dielectric).

PRINCIPLE:PRINCIPLE:

What are Supercapacitors?What are Supercapacitors?Supercapacitors are an advanced version of capacitors with Supercapacitors are an advanced version of capacitors with unique ability to combine energy storage capabilities of unique ability to combine energy storage capabilities of batteries and power storage behavior of capacitor.batteries and power storage behavior of capacitor.Hence fill the gap between batteries and conventional Hence fill the gap between batteries and conventional capacitors such as the electrolyte capacitors in terms of specific capacitors such as the electrolyte capacitors in terms of specific energy as well as specific power.energy as well as specific power.

PROPERTIES OF ENERGY STORAGE PROPERTIES OF ENERGY STORAGE DEVICESDEVICES

50-30050-3000.5-50.5-5<0.01<0.01SPECIFIC ENERGYSPECIFIC ENERGY

( Wh/KG)( Wh/KG)

<500<5001000-30001000-3000> 10,000> 10,000SPECIFIC POWER SPECIFIC POWER (W/KG)(W/KG)

200-1000200-1000101066 - 10 - 1088101066 - 10 - 1088CYCLE LIFECYCLE LIFE

Minutes – monthsMinutes – monthsm sec – minutem sec – minuteμμ sec – m sec sec – m secDISCHARGE TIMEDISCHARGE TIME

HoursHoursm sec - minutem sec - minuteμμ sec – m sec sec – m secCHARGING TIMECHARGING TIME

BATTERYBATTERYEDLCEDLCCAPACITORSCAPACITORSDEVICEDEVICE

TYPES OF SUPERCAPACITORSTYPES OF SUPERCAPACITORS

1.EC DOUBLE LAYER CAPACITORS1.EC DOUBLE LAYER CAPACITORS

The term electrochemical double layer capacitor is most The term electrochemical double layer capacitor is most commonly used for carbon based double layer capacitors commonly used for carbon based double layer capacitors because of its high capacitance value. because of its high capacitance value.

It generally denotes the supercapacitor having non- faradaic It generally denotes the supercapacitor having non- faradaic reactions at both electrodesreactions at both electrodes

CARBON SUPERCAPACITOR

2.PSUEDOCAPACITOR OR 2.PSUEDOCAPACITOR OR ULTRACAPACITORULTRACAPACITOR

In a pseudocapacitor, there are two basic reactions, which In a pseudocapacitor, there are two basic reactions, which lead to electrochemical cell. lead to electrochemical cell.

Both occur at the interface between a conductor and an Both occur at the interface between a conductor and an electrolyte and both benefits form very high specific surface electrolyte and both benefits form very high specific surface areas at the electrode. areas at the electrode.

The first mechanism commonly referred to as charge The first mechanism commonly referred to as charge separation, which is well documented as non-faradaic separation, which is well documented as non-faradaic mechanism and is the basis for EDLC. mechanism and is the basis for EDLC.

The second reaction commonly referred to as an oxidation –The second reaction commonly referred to as an oxidation –reduction reaction due faradaic mechanism.reduction reaction due faradaic mechanism.

HYBRID CAPACITOR:HYBRID CAPACITOR:

Hybrid power system is a new highly reliable Hybrid power system is a new highly reliable energy storage device. It is a combination of EDLC and a energy storage device. It is a combination of EDLC and a battery. (eg. C and Li-ion). Hence it is known as capattery battery. (eg. C and Li-ion). Hence it is known as capattery ((capacapacitor bacitor batteryttery))

WHY “HYBRID”?WHY “HYBRID”?

In supercapacitor two symmetric capacitors are connected in In supercapacitor two symmetric capacitors are connected in series and the total capacitance is halved.series and the total capacitance is halved.

1/C1/Ctotaltotal = 1/C + 1/C = 1/C + 1/C

CCtotaltotal = C/2. = C/2.

But in a hybrid supercapacitor, one of the electrodes is But in a hybrid supercapacitor, one of the electrodes is replaced by a battery electrode. So we can get the total replaced by a battery electrode. So we can get the total capacitance of the single capacitor electrode with the added capacitance of the single capacitor electrode with the added advantage of battery electrode. advantage of battery electrode.

Li-CARBON HYBRID SYSTEMLi-CARBON HYBRID SYSTEM

AIMAIM

Development of hybrid power system combining various Development of hybrid power system combining various power sources with the supercapacitors is the promising field power sources with the supercapacitors is the promising field of research due to its fundamental advantages of both.of research due to its fundamental advantages of both.Our work focuses on developing a hybrid system combining Our work focuses on developing a hybrid system combining Li-ion battery and Carbon based supercapacitor. Li-ion battery and Carbon based supercapacitor. We proposed to study the various supercapacitors based on We proposed to study the various supercapacitors based on cathode material such as LiMncathode material such as LiMn22OO44, LiCoO, LiCoO22, LiFeP, LiFeP22OO77 and and other such materials.other such materials.

CATHODE MATERIALCATHODE MATERIAL

Our work starts with making pure and doped lithium Our work starts with making pure and doped lithium manganate as suitable candidate for Lithium ion based manganate as suitable candidate for Lithium ion based supercapacitor systemsupercapacitor system

Why Lithium manganate ?Why Lithium manganate ?

Spinel LiMnSpinel LiMn22OO44 is of great interest as a is of great interest as a cathode material for lithium ion batteries.cathode material for lithium ion batteries.Advantage:Advantage:

High voltage, low cost and low toxicityHigh voltage, low cost and low toxicityDisadvantage:Disadvantage:

Poor cycling behavior because of a fast capacity fading Poor cycling behavior because of a fast capacity fading due to Jahn Teller distortiondue to Jahn Teller distortion

Average oxidation state of the manganese in Average oxidation state of the manganese in LiMnLiMn22OO44 is 3.5 and thus any small perturbation is 3.5 and thus any small perturbation

influencing the oxidation state may alter the ratio of Mninfluencing the oxidation state may alter the ratio of Mn4+4+ and Mnand Mn3+3+..

When the ratio of MnWhen the ratio of Mn3+3+ increases ,it follows a increases ,it follows a disproportionate reaction disproportionate reaction

2Mn2Mn3+3+ Mn Mn4+4+ + Mn + Mn2+2+

and causes high solubility of spinel material into the and causes high solubility of spinel material into the solution.solution.

JAHN TELLER DISTORTION AND ITS JAHN TELLER DISTORTION AND ITS REMEDYREMEDY

Remedy:Remedy:

Wahihara suggest that partially substituted LiMWahihara suggest that partially substituted LiMxxMnMn1-x1-xOO44 (M=Co, Cu, Ni, Mn) shows improved cyclability due to the (M=Co, Cu, Ni, Mn) shows improved cyclability due to the stronger M-O bonding of octahedron structure in comparison stronger M-O bonding of octahedron structure in comparison to that of Mn-O bonding in LiMnto that of Mn-O bonding in LiMn22OO44..

Hence we studied the both pure and the doped manganate Hence we studied the both pure and the doped manganate systemsystem

SYNTHESIS OF CATHODE MATERIALSYNTHESIS OF CATHODE MATERIALSOL-GEL PROCESS:

LiMn2O4LiCo0.25Cu0.25Ni0.25Mn1.25O4

Li2CO3+MnCO3 in Acetic acidStirring at 500C for 30 minutes

Addition of 50ml of EtOHHeating at 800C for 4 hours

Addition of Ammonia solution(30%)

Addition of 2 X Glycine

Filtering, Drying and Grinding

Heating until gel formation

1.Heating at 5000C for 12 h

2.Firing at 6500C for 12 h

3.Calcining at 7500C for 12h

Physical characterization

Li2CO3+MnCO3+CuCO3+CoCO3+NiCO3

.Ni(OH)3.1.5 H2O in Acetic acid

SEM

XRD

FTIR

SCANNING ELECTRON MICROGRAPHS

LiMn2O4 LiCo0.25Cu0.25Ni0.25Mn1.25O4

X-RAY DIFFRACTIONX-RAY DIFFRACTION

20 30 40 50 60 70 8010

A

B

0

200

400

600

800

1000

1200

1400

1600

1800

2000

A.U

.

2Fig.1. XRD patterns of (A) LiMn2O4 and (B) doped compound.

111311

222

400

331511

440

20 30 40 50 60 70 8010

A

B

0

200

400

600

800

1000

1200

1400

1600

1800

2000

A.U

.

2Fig.1. XRD patterns of (A) LiMn2O4 and (B) doped compound.

20 30 40 50 60 70 8010

A

B

0

200

400

600

800

1000

1200

1400

1600

1800

2000

A.U

.

220 30 40 50 60 70 8010

A

B

0

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20 30 40 50 60 70 8010 20 30 40 50 60 70 8010

A

B

A

B

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1400

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0

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400

600

800

1000

1200

1400

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A.U

.

2Fig.1. XRD patterns of (A) LiMn2O4 and (B) doped compound.

111311

222

400

331511

440

111311

222

400

331511

440

J C P D S # 3 5 - 0 7 8 2 LiMn2o4:

a= 9.412 A0, b= 8.233 A0, c=

4.1002A0, V= 317.73 A0

3

LiCo0.25Cu0.25Ni0.25Mn1.25O4:

a= 8.162, b= 7.0844, c= 6.235 Å

V= 360.6 A03

Pristine LiMnPristine LiMn22OO44 adopts a cubic adopts a cubic Fd3mFd3m space group space group

The XRD data does not shows any structural distortion on The XRD data does not shows any structural distortion on doping which is evident when the doping concentration doping which is evident when the doping concentration increases X<0.5increases X<0.5

FTIR SPECTROGRAPHSFTIR SPECTROGRAPHS

Fig. 2 IR spectra of LiMn2O4 (A) and doped compound (B)

Tran

smitt

ance

%

Wave number, cm-1

1100 1000 900 800 700 600 500 40010

15

20

25

30

35

40

45

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55

60

65

70

75

B

A

Fig. 2 IR spectra of LiMn2O4 (A) and doped compound (B)

Tran

smitt

ance

%

Wave number, cm-1

1100 1000 900 800 700 600 500 40010

15

20

25

30

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B

A

Tran

smitt

ance

%

Wave number, cm-1

1100 1000 900 800 700 600 500 4001000 900 800 700 600 500 40010

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A

B

AA

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 MATERIALANODE MATERIAL

CNF – Carbon Nano FoamCNF – Carbon Nano FoamHigh surface area (1500 m2/g)Low electrical resistanceNo participation in faradaic reactions at the applied voltageHigh capacity (100 - 200 F/g)Unlike AC, CNF combine high surface area with high bulk density to give large capacitance values

CELL FABRICATIONCELL FABRICATION

CONSTITUENTS:CONSTITUENTS:

POSITIVE ELECTRODE POSITIVE ELECTRODE - - LiMnLiMn22OO44(80%)(80%)

CNF(15%)CNF(15%)NMP(5%)NMP(5%)

NEGATIVE ELECTRODE NEGATIVE ELECTRODE - - CNF(95%)CNF(95%)NMP(5%)NMP(5%)

ELECTROLYTEELECTROLYTE -- 1M LiClO1M LiClO4 4 in EC-PCin EC-PC

SEPARATORSEPARATOR -- POLYPROPYLENEPOLYPROPYLENECURRENT COLLECTORCURRENT COLLECTOR -- SSSSELECTRODE AREAELECTRODE AREA -- 1 cm1 cm22

GRINDING AND MIXING AFTER PASTING AND DRYING

COMBINED ELECTRODESCOMPLETE SUPERCAPACITOR

ELECTROCHEMICAL CHARACTERIZATIONELECTROCHEMICAL CHARACTERIZATION

1.1. Electrochemical Impedance Electrochemical Impedance spectroscopyspectroscopy

2.2. Cyclic voltammetryCyclic voltammetry

3.3. Galvanostatic charge / DischargeGalvanostatic charge / Discharge

FOR LiMn2O4: FOR LiCo0.25Cu0.25Ni0.25Mn1.25O4 :

Scan rateScan rate

Material Material 1 mV/s1 mV/s 2 mV/s2 mV/s 5 mV/s5 mV/s

PurePure 3434 3131 2929

DopedDoped 2222 2020 1919

Specific capacitance

(F/g)

= Avg current/scan rate/weight of the material

CYCLIC VOLTAMMETRYCYCLIC VOLTAMMETRY

IMPEDANCE SPECTROSCOPYIMPEDANCE SPECTROSCOPY

5 6 7 8 9 10 11 12 13-1

0

1

2

3

4

5

6

7

8

9

R

C

w

Doped Pure

Z''(

Ohm

)

z'(Ohm)

Impedance parametersImpedance parameters

PARAMETERSPARAMETERS

MATERIALMATERIAL

RRSS (Ohm)(Ohm) RRctct (Ohm)(Ohm) CCdldl (mF/g)(mF/g)

PUREPURE 5.1285.128 0.29170.2917 2.982.98

DOPEDDOPED 5.0435.043 0.23940.2394 3.143.14

CHARGE-DISCHARGECHARGE-DISCHARGE

6300 6350 6400 6450 6500 6550 6600 6650

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Vol

tage

(V)

Time(sec)

DOPED

900 1000 1100 1200 1300 1400 1500 1600

0.0

0.4

0.8

1.2

1.6

2.0

2.4

Volta

ge(V

)

Time (sec)

PURE

FORMULAE USEDFORMULAE USED

Specific Capacitance = Specific Capacitance = Current x Discharge timeCurrent x Discharge timeVoltage x weight

Specific Power = Specific Power = Current x VoltageCurrent x Voltage

weight

Specific Energy = Specific Energy = Current x Voltage x Discharge timeCurrent x Voltage x Discharge time

weight

RESULTSRESULTS

PROPERTYPROPERTY

MATERIALMATERIAL

SPECIFIC SPECIFIC CAPACITANCE CAPACITANCE

(F/g)(F/g)

SPECIFIC SPECIFIC POWER POWER (kW/kg)(kW/kg)

SPECIFIC SPECIFIC ENERGY ENERGY (kWh/kg)(kWh/kg)

LiMnLiMn22OO44 1515 200200 2020

LiCoLiCo0.250.25CuCu0.250.25NiNi0.250.25MnMn11

.25.25OO4466 110110 66

FUTURE WORKFUTURE WORK

Finding the cycle life behavior of this capacitor and Finding the cycle life behavior of this capacitor and variation of properties with cycle life.variation of properties with cycle life.

Continuing the same work for the LiCoOContinuing the same work for the LiCoO22 cathode material cathode material

prepared by various methods and comparing their results prepared by various methods and comparing their results with the results of LiMnwith the results of LiMn22OO44..

THANK YOUTHANK YOU

QUERIES ?QUERIES ?