Tuning electrochemical properties of NaMPO4 nanoparticles for their application in Na-ion supercapacitors.

1. Tuning electrochemical properties of NaMPO4 (M= Mn, Fe)
nanoparticles for their application in Na-ion Supercapacitors.
M.Tech project
Under the supervision of
Prof. Amreesh Chandra
Department of Physics
IIT Kharagpur
By :
Charu Lakshmi T R
15PH62R07
1

2. Introduction
 A supercapacitor is a compact, electrochemical capacitor that
can store an extremely high amount of energy compared to the
conventional capacitor .
 Then it discharges that energy at rates demanded specially by
the application.
 Its capacitance ranges upto 5000 farads.
 Supercapacitors are finding their application in industries
ranging from defence to household appliances, automobiles to
communications, power grids to microelectronics, combustion
engines to rail locomotives
2

3. EDLC & Pseudocapacitor
Fig.1 Schematic representation of EDLC
Source : Wikipedia 3

4. Why NaMPO4 was chosen
 The strong P-O bonds increase the structural stability of the cathode,
characterised by good thermal stability.
 Significantly larger electronegativity of the PO4 groups increases the
ionic character of the M-O bonds.
 This decrease in covalency reduces the separation between the
bonding and antibonding orbitals and translates into an increased cell
potential which helps in tailoring the electrochemical performance of
a material.
( Ref: Materials Today, Volume 19, Number 2,
4

5. Fig.2: Schematic view of the (a) olivine type and (b) maricite-type
structure
Ref: CrytEngComm, 2013,15,9080
- Na ion - Mn ion - Oxygen ion
Schematic view
5

6. NaNO3 +
Mn(NO3)2·4H2O
+ NH4H2PO4
Solution combustion synthesis
of NaMnPO4
6
Stir @ 80˚C and
then add urea &
Set pH to 8
Heat @100 ˚C &
solid mass is
obtained
and then it was subjected to oven heating
@110˚C for 8 hrs + subsequent heating @ 600˚C
for 12 hrs

7. Semi chemical Synthesis of NaFePO4
Fe(NO3)2·4H2O
+ NH4H2PO4
+ NaNO3
Na : Fe : P = 1.05 : 0.97 : 1
7
Solid Mass
obtained
Subject it to oven heating
@ 350˚ C for 4 hrs
+ subsequent heating
@ 650˚ C for 10 hrs
Dissolve in water
& heat @100 ˚ C

8. Synthesis of PANI Coated NaFePO4
Sonicate for 15 min
8
2 gm NaFePO4
in 30 ml
ethanol
+ 10ml water
Add Aniline
Dropwise
Add 10 ml 1M
HCl + APS
Aniline : APS =
4:1
washed & was
collected then heated
@ 60˚c
Stirring
continued in
ice bath for 15
hrs
sonicate for 10 min

9. XRD Analysis
Average crystallite size was calculated using
Scherrer formula
It was approx 10 nm, 34 nm & 29nm for
NaMnPO4, bare and coated NaFePO4
respectively.
Fig.3: XRD of (a)NaMnPO4 (b) NaFePO4 (c) Coated NaFePO4
9
20 25 30 35 40 45
4000
6000
8000
10000
12000
*
*
*
*
*
(222)
(240)
(122)
(221)
(012)
(002)
(031)
(211)
(220)
(121)
(021)
(111)
Intensity(arb.unit)
2 Theta (Degree)
(011)
0 10
0
10
20 30 40 50 60
1600
2000
2400
2800
3200
*
*
*
(022)
(122)
(230)
(200)
(251)
(013)
(400)
(222)
(031)
(211)
(122)
(111)
Intensity(ArbUnit)
2 Theta (Degree)
(020)
20 30 40 50 60
1400
1600
1800
2000
2200
(031)
(211)
(122)
(230)
(200)
(111)
(020)
Intensity(Arb.unit)
2 Theta (Degree)
(a) (b)
(c)

10. FTIR Analysis
 The FTIR
spectrum of
coated NaFePO4
gets modified and
the peaks at
approx 1000 and
3400 cm-1
becomes distinct
as both NaFePO4
and PANI have
similar set of
peaks.
4000 3000 2000 1000 0
NaFePO4
PANI coated NaFePO4
Transmittance(%)
Wave Number (cm-1)
Fig.4: FTIR spectra of NaFePO4 and PANI coated NaFePO4
10

11. SEM images
(a) (b)
Fig.5: SEM images of (a) NaMnPO4
(b)Bare and (c) coated NaFePO4
11
(c)

12. Electrochemical Results of
NaMnPO4
(a)
(b)
Fig.6 : Electrochemical measurements
a) CV curve b) charge-discharge curve
Current
density
(A/g)
Specific
capacitance(F/g)
2 7.009
1 8.198
0.5 10.663
0.25 17.976
12

13. 13Fig. 7 : CV curves for Bare & Coated NaFePO4 in (a)& (b) 2M Na2SO4
and (c)& (d) 2M NaOH
(c)
(b
)
(d)
Electrochemical analysis
0.0 0.2 0.4 0.6 0.8 1.0
-0.0004
-0.0002
0.0000
0.0002
0.0004
0.0006
Current(A)
Voltage (V)
5mV/s (coated)
5mV/s
0.0 0.2 0.4 0.6 0.8 1.0
-0.006
-0.004
-0.002
0.000
0.002
0.004
0.006
Current(A)
Voltage (V)
200mV/s (coated)
200mV/s
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
-0.0005
0.0000
0.0005
0.0010
0.0015
0.0020
Current(A)
Voltage (V)
5mV/s coated
5mV/s
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
-0.008
-0.004
0.000
0.004
0.008
Current(A)
Voltage (V)
200mV/s (coated)
200mV/s
(a)

14. CD curves of Bare & Coated NaFePO4
14
(a)
Fig. 8 : CD curves for bare and coated NaFePO4 in (a)
,(b) 2M Na2SO4 and (c),(d) 2M NaOH
(b)
(c) (d)
0 50 100 150 200 250 300 350
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Voltage(V)
Time (Sec)
0.5 A/g
0.75 A/g
1 A/g
2 A/g
3A/g
0 50 100 150 200 250
-0.4
-0.2
0.0
0.2
0.4
0.6
Voltage(V)
Time (Sec)
0.75A/g
1A/g
2A/g
3/g
0 100 200 300 400 500
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Voltage(V)
Time (Sec)
0.5A/g
0.75A/g
1A/g
2A/g
3A/g
0 50 100 150 200 250 300 350 400
-0.4
-0.2
0.0
0.2
0.4
0.6
Voltage(V)
Time (Sec)
0.5A/g
0.75A/g
1A/g
2A/g
3A/g

15. Current
density
Specific Capacitance (F/g)
a) For
NaFePO4
Pani
coated
b) For
NaFePO4
Pani
coated
0.5A/g 65.78 84.05 57.05 67.25
0.75A/g 54.13 76.03 53.96 66.36
1A/g 50.84 71.85 49.74 59.62
2A/g 29.33 47.30 45.69 58.31
3A/g 20.74 34.74 42.51 57.87
Electrochemical Results
for bare and coated NaFePO4
Specific Capacitance in a) 2M Na2SO4 and b) 2M NaOH 15

16. 0.5 1.0 1.5 2.0 2.5 3.0
20
30
40
50
60
70
80
90
SpecificCapacitance(F/g)
Current Density (A/g)
NaFePO4
Pani Coated NaFePO4
0.5 1.0 1.5 2.0 2.5 3.0
40
45
50
55
60
65
70
SpecificCapacitance(F/g)
Current Density (A/g)
NaFePO4
Pani Coated NaFePO4
Fig.9 (a) Change in specific
capacitance of NaFePO4 for
different scan rates and
Specific capacitance vs. current
density plot of NaFePO4 and PANI
coated NaFePO4
in (b) 2M Na2SO4 and (c) 2M NaOH
electrolyte solution
Change in specific capacitance
16
(a) (b)
0 25 50 75 100 125 150 175 200 225
10
20
30
40
50
60
70
SpecificCapacitance(F/g)
Scan Rate (mV/S)
2 M Na2SO4
2 M NaOH
(c)

17. Cycling stability
0 200 400 600 800 1000
55
60
65
70
SpecificCapacitance(F/g)
Cycle Number
0 200 400 600 800 1000
66
68
70
72
74
76
78
80
SpecificCapacitance(F/g)
Cycle Number
Fig.10 : Cycling curve for (a) NaFePO4 and (b) PANI coated
NaFePO4
• Charging and discharging were carried out at 3A/g for 1000
cycles.
• The capacitance in the first cycle was 62 F/g and 72.8 F/g ,
which remained nearly stable.
17
(a) (b)

18. Conclusions
 NaFePO4 acts as a supercapacitive material in 2M
Na2SO4.
 There was a clear increase in the specific capacitance
of the material after coating with conducting polymer.
 But the capacitance obtained has to be more to
compete with other active materials like the olivines,
spinels, oxides etc.
18

19. Future Aspects
 This being a battery material, much work is not done on
its use as a Supercapacitor electrode material. So,
 The mass loading on the electrode can be reduced, so as
to get higher capacitance.
 Particle size can be tuned further so as to increase the
surface area
 The percentage of monomer used can be varied to find
out the effect on the capacitance.
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20. Acknowledgement
I hereby acknowledge the support of
 Prof. Amreesh Chandra .
 Prof. Krishna Kumar, HOD of physics dept.
 Prof. Achintya Dhar, Facaulty advisor.
 CRF , IIT Kharagpur
 My Labmates; Md. Aqueel Akhtar, Inderjeet Singh, Prasenjit
Haldar, Vikas Sharma, Sudipta Biswas, Ananya
Chowdhury,Debabrata Mandal, Shivangi Shree, Prateek
Srivastava.
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21. Thank you
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